Egwald Economics - Cost Functions: Generalized CES-Translog Cost Function

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Cost Functions

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Elmer G. Wiens

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M. Generalized CES-Translog Cost Function

This web page replicates the procedures used to estimate the parameters of a Translog cost function to approximate a CES cost function. To determine the Translog's efficacy in estimating varying elasticities of substitution among pairs of inputs, on this web page we approximate a Generalized CES cost function with the Translog cost function.

Unlike the CES cost function, the Generalized CES cost function is not necessarily homothetic. Consequently, when we estimate the Translog cost function directly, we do not impose the homothetic conditions as we did when we approximated the CES cost function with the Translog cost function.

The three factor Translog (total) cost function is:

ln(C(q;wL,wK,wM)) = c + cq * ln(q) + cL * ln(wL) + cK * ln(wK) + cM * log(wM)
+ .5 * [dqq * ln(q)^² + dLL * ln(wL)^² + dKK * ln(wK)^² + dMM * ln(wM)^²]
+ .5 * [(dLK + dKL) * ln(wL)*ln(wK) + (dLM + dML) * ln(wL)*ln(wM) + (dKM + dMK) * ln(wK)*log(wM)]
+ dLq * ln(wL)*ln(q) + dKq * ln(wK)*ln(q) + dMq * ln(wM)*ln(q) (**)

an equation linear in its 18 parameters, c, cq, cL, cK, cM, dqq, dLL, dKK, dMM, dLK, dKL, dLM, dML, dKM, dMK, dLq, dKq, and dMq.

We shall use two methods to obtain estimates of the parameters:

À1: Estimate the parameters the cost function by way of its factor share functions — requires data relating output quantities to (cost minimizing) factor inputs, and input prices,

À2: Estimate the parameters of the cost function directly — requires data relating output quantities to total (minimum) cost and input prices.

We shall use the three factor Generalized CES production function to generate the required cost data, yielding a data set relating output, q, and factor prices, wL, wK, and wM, [randomized about the base prices (wL*, wK*, wM*)] to the Generalized CES cost minimizing factor inputs, L, K, and M. The base factor prices and the randomizing distribution are specified in the form below.

The three factor Generalized CES production function is:

q = A * [alpha * L^^-rhoL + beta * K^^-rhoK + gamma *M^^-rhoM]^^(-nu/rho) = f(L,K,M).

where L = labour, K = capital, M = materials and supplies, and q = product.

The parameter nu permits one to adjust the returns to scale, while the parameter rho is the geometric mean of rhoL, rhoK, and rhoM:

rho = (rhoL * rhoK * rhoM)^^1/3.

If rho = rhoL = rhoK = rhoM, we get the standard CES production function. If also, rho = 0, ie sigma = 1/(1+rho) = 1, we get the Cobb-Douglas production function.

Generalized CES Elasticity of Scale of Production:

ε_LKM = ε(L,K,M) = (nu / rho) * (alpha * rhoL * L^^-rhoL + beta * rhoK * K^^-rhoK + gamma * rhoM * M^^-rhoM) / (alpha * L^^-rhoL + beta * K^^-rhoK + gamma * M^^-rhoM).

See the Generalized CES production function.

À1: Estimate the factor share equations separately.

Taking the partial derivative of the cost function, C(q;wL,wK,wM), with respect to an input price, we get the (nonlinear) factor demand function for that input:

∂C/∂wL = L(q; wL, wK, wM),

∂C/∂wK = K(q; wL, wK, wM),

∂C/∂wM = M(q; wL, wK, wM)

The (total) cost of producing q units of output equals the sum of the factor demand functions weighted by their input prices:

C(q;wL,wK,wM) = wL * L(q; wL, wK, wM) + wK * K(q; wL, wK, wM) + wM * M(q; wL, wK, wM),

Write the factor share functions as:

sL(q;wL,wK,wM) = wL * L(q; wL, wK, wM) / C(q;wL,wK,wM) = wL * ∂C/∂wL / C(q;wL,wK,wM) = (∂ln(C)/∂wL )/ (∂ln(wL)/∂wL) = ∂ln(C)/∂ln(wL),

sK(q;wL,wK,wM)= wK * K(q; wL, wK, wM) / C(q;wL,wK,wM) = wK * ∂C/∂wK / C(q;wL,wK,wM) = (∂ln(C)/∂wK )/ (∂ln(wK)/∂wK) = ∂ln(C)/∂ln(wK),

sM(q;wL,wK,wM)= wM * M(q; wL, wK, wM) / C(q;wL,wK,wM) = wM * ∂C/∂wM / C(q;wL,wK,wM) = (∂ln(C)/∂wM )/ (∂ln(wL)/∂wM) = ∂ln(C)/∂ln(wM).

The Translog factor share functions are:

sL(q;wL,wK,wM) = cL + dLq * ln(q) + dLL * ln(wL) + dLK * ln(wK) + dLM * ln(wM),

sK(q;wL,wK,wM) = cK + dKq * ln(q) + dKL * ln(wL) + dKK * ln(wK) + dKM * ln(wM),

sM(q;wL,wK,wM) = cM + dMq * ln(q) + dML * ln(wL) + dMK * ln(wK) + dMM * ln(wM),

three linear equations in their 15 parameters.

Since it is likely that, as measured numerically, dLK != dKL, dLM != dML, and dKM != dMK, these distinctions are maintained in the factor share equations.

Having obtained the unrestricted estimates of the coefficients of the factor share functions, we shall compute the restricted least squares estimates with dLK = dKL, dLM = dML, and dKM = dMK.

I. Stage 1. Obtain the estimates of the fifteen parameters of the three factor share equations using linear multiple regression.

Stage 2. Substitute the values of these parameters into the Translog cost function, and estimate its remaining three parameters, c, cq, and dqq, using linear multiple regression.

II. The estimated coefficients of the Translog cost function will vary with the parameters nu, rho, rhoL, rhoK, rhoM, alpha, beta and gamma of the Generalized CES production function.

Set the parameters below to re-run with your own Generalized CES parameters.

The restrictions ensure that the least-cost problems can be solved to obtain the underlying Generalized CES cost function, using the parameters as specified.
Intermediate (and other) values of the parameters also work.

Restrictions:
.8 < nu < 1.1;
-.6 < rhoL = rho < .6;
-.6 < rho < -.2 → rhoK = .95 * rho, rhoM = rho/.95;
-.2 <= rho < -.1 → rhoK = .9 * rho, rhoM = rho / .9;
-.1 <= rho < 0 → rhoK = .87 * rho, rhoM = rho / .87;
0 <= rho < .1 → rhoK = .7 * rho, rhoM = rho / .7;
.1 <= rho < .2 → rhoK = .67 * rho, rhoM = rho / .67;
.2 <= rho < .6 → rhoK = .6 * rho, rhoM = rho / .6;
rho = 0 → nu = alpha + beta + gamma (Cobb-Douglas)
4 <= wL* <= 11, 7<= wK* <= 16, 4 <= wM* <= 10

Generalized CES Production Function Parameters

nu:

rho:

Base Factor Prices

wL*

wK*

wM*

Distribution to Randomize Factor Prices

Use [-2, 2] Uniform distribution
Use .25 * Normal (μ = 0, σ² = 1)

The Generalized CES production function as specified:

q = 1 * [0.35 * L^^{- 0.17647} + 0.4 * K^^{- 0.11823} + 0.25 *M^^{- 0.26339}]^^(-1/0.17647) = f(L,K,M).

The factor prices are distributed about the base factor prices by adding a random number distributed uniformly in the [-2, 2] domain.

III. For these coefficients of the CES Generalized production function, I generated a sequence (displayed in the "Generalized CES-Translog Cost Function" table) of factor prices, outputs, and the corresponding cost minimizing inputs. Then I used these data to estimate the coefficients of each factor share equation separately:

QR Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
cL	0.361472	0.001	584.346
dLq	-8.7E-5	0	-1.43
dLL	0.034514	0	300.073
dLK	-0.013981	0	-73.532
dLM	-0.02039	0	-230.623

R2 = 0.9999

R2b = 0.9999

# obs = 31

QR Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
cK	0.272471	0.001	385.097
dKq	0.02083	0	297.603
dKL	-0.013871	0	-105.436
dKK	0.030724	0	141.28
dKM	-0.017158	0	-169.678

R2 = 0.9998

R2b = 0.9998

# obs = 31

QR Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
cM	0.366057	0.001	398.769
dMq	-0.020742	0	-228.418
dML	-0.020643	0	-120.944
dMK	-0.016743	0	-59.343
dMM	0.037548	0	286.192

R2 = 0.9999

R2b = 0.9999

# obs = 31

The three estimated factor share functions are:

sL(q;wL,wK,wM) = 0.361472 + -8.7E-5 * ln(q) + 0.034514 * ln(wL) + -0.013981 * ln(wK) + -0.02039 * ln(wM),

sK(q;wL,wK,wM) = 0.272471 + 0.02083 * ln(q) + -0.013871 * ln(wL) + 0.030724 * ln(wK) + -0.017158 * ln(wM),

sM(q;wL,wK,wM) = 0.366057 + -0.020742 * ln(q) + -0.020643 * ln(wL) + -0.016743 * ln(wK) + 0.037548 * ln(wM)

As estimated, generally dLK != dKL, dLM != dML, and dKM != dMK: Young's Theorem doesn't hold without constraints across equations.

Note: C(q;wL,wK,wM) linear homogeneous in factor prices implies:

1 =? cL + cK + cM = 0.361472 + 0.272471 + 0.366057 = 1
0 =? dLL + dLK + dLM = 0.034514 + -0.013981 + -0.02039 = 0.000143
0 =? dKL + dKK + dKM = -0.013871 + 0.030724 + -0.017158 = -0.000305
0 =? dML + dMK + dMM = -0.020643 + -0.016743 + 0.037548 = 0.000162
0 =? dLq + dKq + dMq = -8.7E-5 + 0.02083 + -0.020742 = -0

IV. The Restricted Factor Share Equations.

Having obtained the unrestricted estimates of the coefficients of the factor share functions, we compute the restricted least squares estimates with dLK = dKL, dLM = dML, and dKM = dMK.

QR Restricted Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
cL	0.36145	0.000493	733.833476
dLq	-8.6E-5	7.4E-5	-1.16754
dLL	0.034483	0.000135	255.637251
dLK	-0.013876	0.000118	-117.382613
dLM	-0.020501	8.4E-5	-243.427798
cK	0.272366	0.000717	380.019268
dKq	0.020833	7.3E-5	284.024574
dKL	-0.013876	0.000118	-117.382613
dKK	0.030712	0.000229	134.343624
dKM	-0.017081	9.6E-5	-178.405073
cM	0.366655	0.000429	854.286206
dMq	-0.020764	7.3E-5	-286.149225
dML	-0.020501	8.4E-5	-243.427798
dMK	-0.017081	9.6E-5	-178.405073
dMM	0.037591	0.000104	361.965448

R2 = 1

R2b = 1

# obs = 93

dLK = dKL, dLM = dML, and dKM = dMK

The three estimated, restricted factor share functions are:

sL(q;wL,wK,wM) = 0.36145 + -8.6E-5 * ln(q) + 0.034483 * ln(wL) + -0.013876 * ln(wK) + -0.020501 * ln(wM),

sK(q;wL,wK,wM) = 0.272366 + 0.020833 * ln(q) + -0.013876 * ln(wL) + 0.030712 * ln(wK) + -0.017081 * ln(wM),

sM(q;wL,wK,wM) = 0.366655 + -0.020764 * ln(q) + -0.020501 * ln(wL) + -0.017081 * ln(wK) + 0.037591 * ln(wM)

Imposing the dLK = dKL, dLM = dML, and dKM = dM restrictions may distort five necessary C(q;wL,wK,wM) linear homogeneous in factor prices restraints:

1 =? cL + cK + cM = 0.36145 + 0.272366 + 0.366655 = 1.000471
0 =? dLL + dLK + dLM = 0.034483 + -0.013876 + -0.020501 = 0.000107
0 =? dKL + dKK + dKM = -0.013876 + 0.030712 + -0.017081 = -0.000246
0 =? dML + dMK + dMM = -0.020501 + -0.017081 + 0.037591 = 9.0E-6
0 =? dLq + dKq + dMq = -8.6E-5 + 0.020833 + -0.020764 = -1.7E-5

Let us impose these additional five restraints and re-estimate the Restricted Factor Share Equations:

QR Restricted Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
cL	0.361598	0.000223	1621.747514
dLq	-7.6E-5	6.0E-5	-1.254166
dLL	0.034398	8.0E-5	429.596417
dLK	-0.013861	8.0E-5	-174.166234
dLM	-0.020537	5.8E-5	-353.753838
cK	0.271773	0.000235	1158.319087
dKq	0.020834	6.0E-5	346.378655
dKL	-0.013861	8.0E-5	-174.166234
dKK	0.030909	0.000115	268.172655
dKM	-0.017048	7.4E-5	-231.851127
cM	0.366629	0.000216	1698.979294
dMq	-0.020758	6.0E-5	-347.343655
dML	-0.020537	5.8E-5	-353.753838
dMK	-0.017048	7.4E-5	-231.851127
dMM	0.037585	7.4E-5	508.139524

R2 = 1

R2b = 1

# obs = 93

dLK = dKL, dLM = dML, dKM = dMK
1 = cL + cK + cM
0 = dLL + dLK + dLM
0 = dKL + dKK + dKM
0 = dML + dMK + dMM
0 = dLq + dKq + dMq

The three re-estimated, restricted factor share functions are:

sL(q;wL,wK,wM) = 0.361598 + -7.6E-5 * ln(q) + 0.034398 * ln(wL) + -0.013861 * ln(wK) + -0.020537 * ln(wM),

sK(q;wL,wK,wM) = 0.271773 + 0.020834 * ln(q) + -0.013861 * ln(wL) + 0.030909 * ln(wK) + -0.017048 * ln(wM),

sM(q;wL,wK,wM) = 0.366629 + -0.020758 * ln(q) + -0.020537 * ln(wL) + -0.017048 * ln(wK) + 0.037585 * ln(wM)

V. To obtain estimates of the remaining three parameters, c, cq, and dqq, write:

ln(C(q;wL,wK,wM)) - {cL * ln(wL) + cK * ln(wK) + cM * log(wM) + .5 * [dLL * ln(wL)^² + dKK * ln(wK)^² + dMM * ln(wM)^²]
+ .5 * [(dLK + dKL) * ln(wL)*ln(wK) + (dLM + dML) * ln(wL)*ln(wM) + (dKM + dMK) * ln(wK)*log(wM)]
+ dLq * ln(wL)*ln(q) + dKq * ln(wK)*ln(q) + dMq * ln(wM)*ln(q)}
= R(q;wL,wK,wM) = c + cq * ln(q) + .5 * dqq * ln(q)^²

Estimate the linear equation:

R(q;wL,wK,wM) = c + cq * ln(q) + .5 * dqq * ln(q)^²

to obtain c, cq, and dqq.

QR Restricted Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
c	1.115696	0.000134	8329.399415
cq	1	0	1000
dqq	0.020897	2.2E-5	950.983981

R2 = 1

R2b = 1

# obs = 31

1 = cq

VI. The Translog cost function as estimated is:

ln(C(q;wL,wK,wM)) = 1.115696 + 1 * ln(q) + 0.361598 * ln(wL) + 0.271773 * ln(wK) + 0.366629 * log(wM)
+ .5 * [0.020897 * ln(q)^² + 0.034398 * ln(wL)^² + 0.030909 * ln(wK)^² + 0.037585 * ln(wM)^²]
+ .5 * [-0.027722 * ln(wL)*ln(wK) + -0.041075 * ln(wL)*ln(wM) + -0.034096 * ln(wK)*log(wM)]
+ -7.6E-5 * ln(wL)*ln(q) + 0.020834 * ln(wK)*ln(q) + -0.020758 * ln(wM)*ln(q) (***)

VII. Check for linear homogeneity:

1 =? cL + cK + cM = 0.361598 + 0.271773 + 0.366629 = 1
0 =? dLL + dLK + dLM = 0.034398 + -0.013861 + -0.020537 = 0
0 =? dKL + dKK + dKM = -0.013861 + 0.030909 + -0.017048 = 0
0 =? dML + dMK + dMM = -0.020537 + -0.017048 + 0.037585 = 0
0 =? dLq + dKq + dMq = -7.6E-5 + 0.020834 + -0.020758 = 0

C(q;wL,wK,wM) linear homogeneous in factor prices requires for any t > 0, that C(q;wL,wK,wM) obey:

C(q;t*wL,t*wK,t*wM) = t * C(q;wL,wK,wM)

For example, with wL = 7, wK = 13, wM = 6, and t = 2:

2 * C(25; 7, 13, 6) = 1412.93 =? 1412.93 = C(25; 14, 26,12).

2 * C(30; 7, 13, 6) = 1722.08 =? 1722.08 = C(30; 14, 26,12).

VIII. Check for homotheticity:

Can we write C(q;wL,wK,wM) as the product of the unit cost function C(1;wL,wK,wM) and a suitable increasing function h(q) with h(0) = 0, and h(1) = 1:

C(q;wL,wK,wM) =? h(q) * C(1;wL,wK,wM)

To do so it is necessary that:

1 =? cq = 1, 0 =? dqq = 0.020897,

0 =? dLq = -7.6E-5, 0 =? dKq = 0.020834, 0 =? dMq = -0.020758.

For example, with wL = 7, wK = 13, wM = 6, and q = 30, try h(q) = q^1/nu with nu = 1:

C(30; 7, 13, 6) = 861.04 =? 722.36 = 30 * 24.08 = 30^^1/1 * C(1; 7, 13, 6).

Try it with rho = 0!

IX. 1. The matrix ∇²C of second order partial derivatives of the cost function C(q;wL,wK,wM) is symmetric. To show this, write:

ln(C(q;wL,wK,wM) = C(q;wL,wK,wM), so C(q;wL,wK,wM) = exp(C(q;wL,wK,wM)).

∂²C/∂q∂wL = dLq/(q*wL) = ∂²C/∂wL∂q,

∂²C/∂q∂wK = dKq/(q*wK) = ∂²C/∂wK∂q,

∂²C/∂q∂wM = dMq/(q*wM) = ∂²C/∂wM∂q,

∂²C/∂wL∂wK = .25 * (dLK+dKL)/(wL*wK) = ∂²C/∂wK∂wL,

∂²C/∂wL∂wM = .25 * (dLM+dML)/(wL*wM) = ∂²C/∂wM∂wL,

∂²C/∂wK∂wM = .25 * (dKM+dMK)/(wL*wK) = ∂²C/∂wM∂wK.

Since the matrix ∇²C(q;wL,wK,wM) is symmetric, the matrix ∇²C(q;wL,wK,wM) is also symmetric.

2. The cost function C(q;wL,wK,wM) is a concave in factor prices if its Hessian matrix ∇²_wwC of second order partial derivatives with respect to factor prices is negative semidefinite. Following the procedure suggested by Diewert and Wales (1987), write sL = sL(q;wL,wK,wM), sK = sK(q;wL,wK,wM), and sM = sM(q;wL,wK,wM), and the matrices:

D =

dLL	dLK	dLM
dKL	dKK	dKM
dML	dMK	dMM

S =

sL	0	0
0	sK	0
0	0	sM

SS =

sL*sL	sL*sK	sL*sM
sK*sL	sK*sK	sK*sM
sM*sL	sM*sK	sM*sM

W =

wL	0	0
0	wK	0
0	0	wM

Assuming C(q;wL,wK,wM) > 0, then ∇²_wwC is negative semidefinite if and only if the matrix:

H = W * ∇²_wwC * W = D - S + SS

is negative semidefinite. See the Mathematical Notes.

The values of the second order partial derivatives depend on the amount of output, and on factor prices. As an example, consider the case where q = 30, wL = 7, wK = 13, and wM = 6:

W * ∇²_wwC * W =

-0.19484	0.11584	0.07901
0.11584	-0.2007	0.08487
0.07901	0.08487	-0.16387

The principal minors of H are H1 = -0.194844, H2 = 0.025688, and H3 = 0.

If these principal minors alternate in sign, starting with negative, with H3 <= 0, the matrix H is negative (semi)definite,
and the cost function C(q;wL,wK,wM) is a concave function in factor prices at q = 30, wL = 7, wK = 13, and wM = 6.

The eigenvalues of H are e1 = -0.314, e2 = -0.2454, and e3 = 0.
H3 = e1 * e2 * e3 = 0.

X. The three estimated factor demand functions are obtained by:

L(q;wL,wK,wM) = sL(q;wL,wK,wM) * C(q;wL,wK,wM) / wL,

K(q;wL,wK,wM) = sK(q;wL,wK,wM) * C(q;wL,wK,wM) / wK,

M(q;wL,wK,wM) = sM(q;wL,wK,wM) * C(q;wL,wK,wM) / wM.

The estimated factor demand elasticities are obtained by:

ε_L,wL = ∂ln(L(q;wL,wK,wM))/∂ln(wL) = -1 + sL(q;wL,wK,wM) + dLL / sL(q;wL,wK,wM),

ε_L,wK = ∂ln(L(q;wL,wK,wM))/∂ln(wK) = sK(q;wL,wK,wM) + dLK / sL(q;wL,wK,wM),

ε_L,wM = ∂ln(L(q;wL,wK,wM))/∂ln(wM) = sM(q;wL,wK,wM) + dLM / sL(q;wL,wK,wM),

ε_L,q = ∂ln(L(q;wL,wK,wM))/∂ln(q) = q * ∂ln(C)/∂q + dLq / sL(q;wL,wK,wM), etc.

For example, with wL = 7, wK = 13, wM = 6, and q = 30:

ε_L,wL	ε_L,wK	ε_L,wM	ε_L,q
ε_K,wL	ε_K,wK	ε_K,wM	ε_K,q
ε_M,wL	ε_M,wK	ε_M,wM	ε_M,q

-0.5474	0.3255	0.222	1.087
0.3179	-0.5508	0.2329	1.1443
0.2825	0.3034	-0.5859	1.013

XI. Uzawa Partial Elasticities of Substitution:

u_LK = C(q;wL,wK,wM) * ∂L(q;wL,wK,wM)/∂wK / (L(q;wL,wK,wM) * K(q;wL,wK,wM)),

u_LM = C(q;wL,wK,wM) * ∂L(q;wL,wK,wM)/∂wM / (L(q;wL,wK,wM) * M(q;wL,wK,wM)),

u_KL = C(q;wL,wK,wM) * ∂K(q;wL,wK,wM)/∂wL / (K(q;wL,wK,wM) * L(q;wL,wK,wM)),

u_KM = C(q;wL,wK,wM) * ∂K(q;wL,wK,wM)/∂wM / (K(q;wL,wK,wM) * M(q;wL,wK,wM)),

u_ML = C(q;wL,wK,wM) * ∂M(q;wL,wK,wM)/∂wL / (M(q;wL,wK,wM) * L(q;wL,wK,wM)),

u_MK = C(q;wL,wK,wM) * ∂M(q;wL,wK,wM)/∂wK / (M(q;wL,wK,wM) * K(q;wL,wK,wM)),

where the partial derivatives of the factor demand functions are:

∂L(q;wL,wK,wM)/∂wK = (dLK * C / wK + sL * K) * C / (wL * L * K),

∂L(q;wL,wK,wM)/∂wM = (dLM * C / wM + sL * M) * C / (wL * L * M),

∂K(q;wL,wK,wM)/∂wL = (dKL * C / wL + sK * L) * C / (wK * K * L),

∂K(q;wL,wK,wM)/∂wM = (dKM * C / wM + sK * M) * C / (wK * K * M),

∂M(q;wL,wK,wM)/∂wL = (dML * C / wL + sM * L) * C / (wM * M * K),

∂M(q;wL,wK,wM)/∂wK = (dMK * C / wK + sM * K) * C / (wM * M * L)

With the dLK = dKL, dLM = dML, and dKM = dMK restrictions in the factor share functions, we get equality of the cross partial elasticities of substitution:

u_LK = u_KL, u_LM = u_ML, and u_KM = u_MK.

as seen in the following table.

XII. Table of Results: check that the estimated Translog cost function and input amounts for a given level of output agree with the Generalized CES production function's minimized cost and inputs. Also, compare the Allen partial elasticities of substitution, s_LK, s_LM, and s_MK, with the Uzawa partial elasticities of substitution, u_LK, u_LM, and u_KM.

Generalized CES-Translog Cost Function À1: Estimate the Translog cost function using restricted factor shares Parameters: nu = 1, rho = 0.17647, rhoL = 0.17647, rhoK = 0.11823, rhoM = 0.26339
					— Generalized CES Cost Data —								— Translog Cost Data —				Factor Shares			Uzawa Elasticities						W * ∇²_wwC * W
obs #	q	wL	wK	wM	L	K	M	s_LK	s_LM	s_KM	ε_LKM	cost	est cost	est L	est K	est M	sL	sK	sM	u_LK	u_LM	u_KL	u_KM	u_ML	u_MK	e₁	e₂	e₃
1	18	5.68	12.08	5.64	27.19	12.95	22.92	0.9	0.79	0.83	0.927	440.19	440.34	27.22	12.96	22.92	0.351	0.355	0.293	0.89	0.8	0.89	0.84	0.8	0.84	-0.307	-0.254	0
2	19	7.78	11.98	4.9	23.46	14.8	28.64	0.9	0.79	0.83	0.924	500.13	500.26	23.46	14.8	28.67	0.365	0.354	0.281	0.89	0.8	0.89	0.83	0.8	0.83	-0.313	-0.247	0
3	20	7.08	11.66	4.3	25.13	14.99	31.43	0.89	0.79	0.83	0.922	487.84	487.92	25.13	14.99	31.45	0.365	0.358	0.277	0.89	0.8	0.89	0.83	0.8	0.83	-0.315	-0.244	0
4	21	5.04	14.22	5.5	35.98	13.51	27.6	0.9	0.79	0.83	0.922	525.2	525.26	35.98	13.51	27.6	0.345	0.366	0.289	0.89	0.79	0.89	0.84	0.79	0.84	-0.31	-0.251	0
5	22	6.68	14.48	6.98	34.39	16.3	27.39	0.9	0.79	0.83	0.925	657.03	657.05	34.4	16.31	27.39	0.35	0.359	0.291	0.89	0.8	0.89	0.84	0.8	0.84	-0.309	-0.253	0
6	23	5.5	12.5	6.84	38.15	17.43	26.29	0.9	0.79	0.83	0.927	607.56	607.54	38.16	17.44	26.27	0.346	0.359	0.296	0.89	0.8	0.89	0.84	0.8	0.84	-0.306	-0.255	0
7	24	7.04	12.88	4.06	31.36	17.22	40.23	0.89	0.79	0.83	0.916	605.86	605.81	31.35	17.22	40.24	0.364	0.366	0.27	0.9	0.79	0.9	0.83	0.79	0.83	-0.319	-0.239	0
8	25	5.26	11.86	6.16	41.07	18.97	29.53	0.9	0.79	0.83	0.925	622.9	622.85	41.07	18.97	29.51	0.347	0.361	0.292	0.89	0.8	0.89	0.84	0.8	0.84	-0.308	-0.253	0
9	26	5.18	14.96	8	49.54	18.52	28.25	0.9	0.79	0.83	0.925	759.67	759.58	49.52	18.53	28.22	0.338	0.365	0.297	0.89	0.8	0.89	0.84	0.8	0.84	-0.307	-0.255	0
10	27	6.44	13.5	5.96	41.33	20.38	35.78	0.89	0.79	0.83	0.921	754.55	754.46	41.32	20.38	35.78	0.353	0.365	0.283	0.89	0.79	0.89	0.83	0.79	0.83	-0.313	-0.247	0
11	28	7.08	11.46	4.9	37.07	22.91	40.7	0.89	0.79	0.83	0.919	724.4	724.28	37.06	22.9	40.71	0.362	0.362	0.275	0.89	0.79	0.89	0.83	0.79	0.83	-0.316	-0.243	0
12	29	8.98	13.54	5.56	36.74	24.18	44.08	0.89	0.79	0.83	0.918	902.42	902.26	36.72	24.18	44.09	0.365	0.363	0.272	0.9	0.79	0.9	0.83	0.79	0.83	-0.318	-0.24	0
13	30	7	13	6	43.79	24.14	40.13	0.89	0.79	0.83	0.92	861.17	861.04	43.78	24.14	40.14	0.356	0.364	0.28	0.89	0.79	0.89	0.83	0.79	0.83	-0.314	-0.245	0
14	31	6.72	14.84	7.98	51.67	24.61	36.17	0.9	0.79	0.83	0.922	1001.05	1000.91	51.66	24.61	36.16	0.347	0.365	0.288	0.89	0.79	0.89	0.84	0.79	0.84	-0.31	-0.25	0
15	32	5.56	14.14	5.78	54.38	22.89	42.14	0.89	0.79	0.83	0.917	869.62	869.5	54.36	22.89	42.16	0.348	0.372	0.28	0.89	0.79	0.89	0.84	0.79	0.84	-0.314	-0.245	0
16	33	6.7	13.96	4.32	47.47	23.71	54.2	0.89	0.79	0.83	0.911	883.23	883.09	47.47	23.71	54.18	0.36	0.375	0.265	0.9	0.78	0.9	0.83	0.78	0.83	-0.321	-0.235	0
17	34	5.76	11.48	7.96	57.21	30.02	35.26	0.9	0.79	0.83	0.925	954.88	954.76	57.21	30.03	35.24	0.345	0.361	0.294	0.89	0.8	0.89	0.84	0.8	0.84	-0.307	-0.254	0
18	35	6.1	13.32	6.1	56.52	27.32	45.05	0.89	0.79	0.83	0.917	983.43	983.32	56.5	27.31	45.06	0.351	0.37	0.28	0.89	0.79	0.89	0.84	0.79	0.84	-0.314	-0.245	0
19	36	5.72	12.36	6.6	59.96	29.35	42.5	0.89	0.79	0.83	0.92	986.21	986.13	59.94	29.35	42.51	0.348	0.368	0.284	0.89	0.79	0.89	0.84	0.79	0.84	-0.312	-0.248	0
20	37	8.58	13.12	4.46	46.42	30.54	62.95	0.89	0.79	0.83	0.912	1079.75	1079.65	46.42	30.55	62.9	0.369	0.371	0.26	0.9	0.79	0.9	0.82	0.79	0.82	-0.324	-0.232	0
21	38	5.82	11.9	5.94	60.76	31.27	47.42	0.89	0.79	0.83	0.918	1007.36	1007.31	60.75	31.26	47.43	0.351	0.369	0.28	0.89	0.79	0.89	0.83	0.79	0.83	-0.314	-0.245	0
22	39	7.84	11.18	6.96	53.87	38.02	47.34	0.89	0.79	0.83	0.921	1176.89	1176.86	53.87	38.01	47.35	0.359	0.361	0.28	0.89	0.8	0.89	0.83	0.8	0.83	-0.314	-0.246	-0
23	40	5.44	13.72	5.74	69.42	29.82	52.28	0.89	0.79	0.83	0.914	1086.87	1086.86	69.41	29.81	52.32	0.347	0.376	0.276	0.89	0.79	0.89	0.84	0.79	0.84	-0.316	-0.242	0
24	41	8.34	13.52	4.26	52.79	33.18	71.94	0.89	0.79	0.83	0.909	1195.32	1195.37	52.8	33.2	71.85	0.368	0.376	0.256	0.9	0.78	0.9	0.82	0.78	0.82	-0.326	-0.229	0
25	42	6.58	13.34	5.46	64.62	33.61	59.15	0.89	0.79	0.83	0.913	1196.47	1196.51	64.62	33.61	59.16	0.355	0.375	0.27	0.9	0.79	0.9	0.83	0.79	0.83	-0.319	-0.239	0
26	43	8.62	11.14	5.38	53.77	41.44	62.45	0.89	0.79	0.83	0.915	1261.14	1261.2	53.76	41.45	62.47	0.367	0.366	0.266	0.9	0.79	0.9	0.83	0.79	0.83	-0.32	-0.237	0
27	44	7.06	11.84	4.22	59.57	36.56	71.09	0.89	0.79	0.83	0.91	1153.47	1153.59	59.59	36.57	71.05	0.365	0.375	0.26	0.9	0.78	0.9	0.83	0.78	0.83	-0.324	-0.232	0
28	45	5.66	14.64	4.16	73.81	31.09	73.7	0.89	0.79	0.83	0.906	1179.58	1179.69	73.88	31.08	73.68	0.354	0.386	0.26	0.9	0.78	0.9	0.83	0.78	0.83	-0.324	-0.231	0
29	46	7.3	14.58	5.2	68.79	36.38	70.75	0.89	0.79	0.83	0.909	1400.46	1400.68	68.82	36.38	70.74	0.359	0.379	0.263	0.9	0.78	0.9	0.83	0.78	0.83	-0.323	-0.233	0
30	47	6.1	11.18	5.24	71.18	40.72	62.97	0.89	0.79	0.83	0.914	1219.47	1219.72	71.19	40.73	63	0.356	0.373	0.271	0.9	0.79	0.9	0.83	0.79	0.83	-0.319	-0.239	0
31	48	8.12	12.48	7.78	70.36	47.09	57.14	0.89	0.79	0.83	0.918	1603.57	1603.98	70.37	47.1	57.18	0.356	0.366	0.277	0.89	0.79	0.89	0.83	0.79	0.83	-0.315	-0.244	0
AVE:	33	6.67	12.93	5.75	49.61	26.58	45.72	0.89	0.79	0.83	0.918	925.41	925.41	49.61	26.58	45.72	0.355	0.367	0.278	0.89	0.79	0.89	0.83	0.79	0.83	-0.315	-0.244	0

À2: Estimating the Translog cost function directly.

XIII. If we have a data set relating the input (factor) prices, wL, wK, and wM, to the total (minimum) cost of producing output for varying levels output, but we do not have data on the required levels of inputs, we can estimate the Translog cost function directly. We will use the same sequence (displayed in the "Generalized CES-Translog Cost Function" table) of factor prices, outputs, and total (minimum) cost as used in À1. The estimated coefficients of the cost function will vary with the parameters nu, rho, rhoL, rhoK, rhoM, alpha, beta and gamma of the Generalized CES production function used to generate these data. We impose 5 restrictions on the estimates of the parameters as specified:

SVD Restricted Least Squares
Parameter Estimates
Parameter	Coefficient	std error	t-ratio
c	1.094091	0.000583	1876.99773
cq	1.012881	0.000317	3196.373152
cL	0.361717	0.000281	1288.735631
cK	0.271277	0.000408	665.241071
cM	0.367006	0.000278	1319.99443
dqq	0.017099	9.1E-5	187.915395
dLL	0.034412	0.00016	214.774107
dKK	0.031209	0.000215	145.080693
dMM	0.037613	0.000122	307.585406
2*dLK	-0.028008	0.000316	-88.601649
2*dLM	-0.040816	0.000186	-218.854745
2*dKM	-0.03441	0.000259	-132.652774
dLq	-0.000148	0.00013	-1.138496
dKq	0.041833	0.000186	225.255437
dMq	-0.041685	0.000139	-298.963689

R2 = 1	R2b = 1	# obs = 31
Observation Matrix Rank: 15

1 = cL + cK + cM
0 = dLL + dLK + dLM
0 = dKL + dKK + dKM
0 = dML + dMK + dMM
0 = dLq + dKq + dMq

XIV. The Translog cost function estimated directly is:

ln(C(q;wL,wK,wM)) = 1.094091 + 1.012881 * ln(q) + 0.361717 * ln(wL) + 0.271277 * ln(wK) + 0.367006 * log(wM)
+ .5 * [0.017099 * ln(q)^² + 0.034412 * ln(wL)^² + 0.031209 * ln(wK)^² + 0.037613 * ln(wM)^²]
+ .5 * [-0.028008 * ln(wL)*ln(wK) + -0.040816 * ln(wL)*ln(wM) + -0.03441 * ln(wK)*log(wM)]
+ -0.000148 * ln(wL)*ln(q) + 0.041833 * ln(wK)*ln(q) + -0.041685 * ln(wM)*ln(q) (***)

XV. Its three derived factor share functions are:

sL(q;wL,wK,wM) = 0.361717 + -0.000148 * ln(q) + 0.034412 * ln(wL) + -0.014004 * ln(wK) + -0.020408 * ln(wM),

sK(q;wL,wK,wM) = 0.271277 + 0.041833 * ln(q) + -0.014004 * ln(wL) + 0.031209 * ln(wK) + -0.017205 * ln(wM),

sM(q;wL,wK,wM) = 0.367006 + -0.041685 * ln(q) + -204.08 * ln(wL) + -0.017205 * ln(wK) + 0.037613 * ln(wM)

XVI. Notes:
1. As derived, dLK = dKL, dLM = dML, and dKM = dMK: Young's Theorem holds by construction.

2. C(q;wL,wK,wM) linear homogeneous in factor prices implies:

1 =? cL + cK + cM = 0.361717 + 0.271277 + 0.367006 = 1
0 =? dLL + dLK + dLM = 0.034412 + -0.014004 + -0.020408 = 0
0 =? dKL + dKK + dKM = -0.014004 + 0.031209 + -0.017205 = -0
0 =? dML + dMK + dMM = -0.020408 + -0.017205 + 0.037613 = -0
0 =? dLq + dKq + dMq = -0.000148 + 0.041833 + -0.041685 = -0

3. The matrix ∇²C of second order partial derivatives of the cost function C(q;wL,wK,wM) is symmetric.

4. The cost function C(q;wL,wK,wM) is a concave in factor prices if its Hessian matrix ∇²_wwC of second order partial derivatives with respect to factor prices is negative semidefinite. Following the procedure suggested by Diewert and Wales (1987), write sL = sL(q;wL,wK,wM), sK = sK(q;wL,wK,wM), and sM = sM(q;wL,wK,wM), and the matrices:

D =

dLL	dLK	dLM
dKL	dKK	dKM
dML	dMK	dMM

S =

sL	0	0
0	sK	0
0	0	sM

SS =

sL*sL	sL*sK	sL*sM
sK*sL	sK*sK	sK*sM
sM*sL	sM*sK	sM*sM

W =

wL	0	0
0	wK	0
0	0	wM

Assuming C(q;wL,wK,wM) > 0, then ∇²_wwC is negative semidefinite if and only if the matrix:

H = W * ∇²_wwC * W = D - S + SS

is negative semidefinite. See the Mathematical Notes.

The values of the second order partial derivatives depend on the amount of output, and on factor prices. As an example, consider the case where q = 30, wL = 7, wK = 13, and wM = 6:

W * ∇²_wwC * W =

-0.19476	0.14091	0.05385
0.14091	-0.21463	0.07372
0.05385	0.07372	-0.12758

The principal minors of H are H1 = -0.194763, H2 = 0.021947, and H3 = -0.

If these principal minors alternate in sign, starting with negative, with H3 <= 0, the matrix H is negative (semi)definite,
and the cost function C(q;wL,wK,wM) is a concave function in factor prices at q = 30, wL = 7, wK = 13, and wM = 6.

The eigenvalues of H are e1 = -0.3475, e2 = -0.1895, and e3 = -0.
H3 = e1 * e2 * e3 = -0.

XVII. Check for linear homogeneity:

C(q;wL,wK,wM) linear homogeneous in factor prices requires for any t > 0, that C(q;wL,wK,wM) obey:

C(q;t*wL,t*wK,t*wM) = t * C(q;wL,wK,wM)

For example, with wL = 7, wK = 13, wM = 6, and t = 2:

2 * C(25; 7, 13, 6) = 1488.51 =? 1488.51 = C(25; 14, 26,12).

2 * C(30; 7, 13, 6) = 1819.68 =? 1819.68 = C(30; 14, 26,12).

XVIII. Check for homotheticity:

Can we write C(q;wL,wK,wM) as the product of the unit cost function C(1;wL,wK,wM) and a suitable increasing function h(q) with h(0) = 0, and h(1) = 1:

C(q;wL,wK,wM) =? h(q) * C(1;wL,wK,wM)

To do so it is necessary that:

1 =? cq = 1.012881, 0 =? dqq = 0.017099,

0 =? dLq = -0.000148, 0 =? dKq = 0.041833, 0 =? dMq = -0.041685.

As examples:

a. with wL = 7, wK = 13, wM = 6, and q = 25, try h(q) = q^1/nu with nu = 1:

C(25; 7, 13, 6) = 744.26 =? 588.93 = 25 * 23.56 = 25^^1/1 * C(1; 7, 13, 6).

b. with wL = 7, wK = 13, wM = 6, and q = 30, try h(q) = q^1/nu with nu = 1:

C(30; 7, 13, 6) = 909.84 =? 706.71 = 30 * 23.56 = 30^^1/1 * C(1; 7, 13, 6).

Try it with rho = 0!

XIX. The three derived factor demand functions are obtained by:

L(q;wL,wK,wM) = sL(q;wL,wK,wM) * C(q;wL,wK,wM) / wL,

K(q;wL,wK,wM) = sK(q;wL,wK,wM) * C(q;wL,wK,wM) / wK,

M(q;wL,wK,wM) = sM(q;wL,wK,wM) * C(q;wL,wK,wM) / wM.

The factor demand elasticities are obtained by:

For example, with wL = 7, wK = 13, wM = 6, and q = 30:

ε_L,wL	ε_L,wK	ε_L,wM	ε_L,q
ε_K,wL	ε_K,wK	ε_K,wM	ε_K,q
ε_M,wL	ε_M,wK	ε_M,wM	ε_M,q

-0.5476	0.3962	0.1514	1.1029
0.3235	-0.4928	0.1693	1.1994
0.2579	0.3531	-0.6111	0.9037

XX. Table of Results: check that the estimated Translog cost function and input amounts for a given level of output agree with the Generalized CES production function's minimized cost and inputs. Also, compare the Allen partial elasticities of substitution, s_LK, s_LM, and s_MK, with the Uzawa partial elasticities of substitution, u_LK, u_LM, and u_KM. Comparing the estimated cost and input amounts obtained from the Translog cost function with the Generalized CES data, one can conclude that method À1 obtains more accurate results than method À2 for rho > 0.

Generalized CES-Translog Cost Function À2: Estimate the Translog cost function directly Parameters: nu = 1, rho = 0.17647, rhoL = 0.17647, rhoK = 0.11823, rhoM = 0.26339
				— Generalized CES Cost Data —								— Translog Cost Data —				Factor Shares			Uzawa Elasticities						W * ∇²_wwC * W
obs #	q	wL	wK	wM	L	K	M	s_LK	s_LM	s_KM	ε_LKM	cost	est cost	est L	est K	est M	sL	sK	sM	u_LK	u_LM	u_KL	u_KM	u_ML	u_MK	e₁	e₂	e₃
1	18	5.68	12.08	5.64	27.19	12.95	22.92	0.9	0.79	0.83	0.927	440.19	460.93	28.47	15.87	19.06	0.351	0.416	0.233	0.9	0.75	0.9	0.82	0.75	0.82	-0.336	-0.21	-0
2	19	7.78	11.98	4.9	23.46	14.8	28.64	0.9	0.79	0.83	0.924	500.13	528.39	24.77	18.34	23.66	0.365	0.416	0.219	0.91	0.74	0.91	0.81	0.74	0.81	-0.343	-0.199	-0
3	20	7.08	11.66	4.3	25.13	14.99	31.43	0.89	0.79	0.83	0.922	487.84	519.24	26.73	18.74	25.94	0.364	0.421	0.215	0.91	0.74	0.91	0.81	0.74	0.81	-0.345	-0.195	-0
4	21	5.04	14.22	5.5	35.98	13.51	27.6	0.9	0.79	0.83	0.922	525.2	557.97	38.19	16.85	22.88	0.345	0.43	0.226	0.91	0.74	0.91	0.82	0.74	0.82	-0.34	-0.203	-0
5	22	6.68	14.48	6.98	34.39	16.3	27.39	0.9	0.79	0.83	0.925	657.03	688.78	36.04	20.17	22.35	0.35	0.424	0.226	0.91	0.74	0.91	0.82	0.74	0.82	-0.339	-0.204	-0
6	23	5.5	12.5	6.84	38.15	17.43	26.29	0.9	0.79	0.83	0.927	607.56	632.09	39.68	21.46	21.29	0.345	0.424	0.23	0.9	0.74	0.9	0.82	0.74	0.82	-0.338	-0.207	-0
7	24	7.04	12.88	4.06	31.36	17.22	40.23	0.89	0.79	0.83	0.916	605.86	654.09	33.82	21.97	32.77	0.364	0.433	0.203	0.91	0.72	0.91	0.8	0.72	0.8	-0.35	-0.185	-0
8	25	5.26	11.86	6.16	41.07	18.97	29.53	0.9	0.79	0.83	0.925	622.9	651.01	42.9	23.53	23.76	0.347	0.429	0.225	0.91	0.74	0.91	0.82	0.74	0.82	-0.34	-0.202	-0
9	26	5.18	14.96	8	49.54	18.52	28.25	0.9	0.79	0.83	0.925	759.67	792.85	51.66	22.96	22.72	0.338	0.433	0.229	0.9	0.74	0.9	0.83	0.74	0.83	-0.338	-0.205	-0
10	27	6.44	13.5	5.96	41.33	20.38	35.78	0.89	0.79	0.83	0.921	754.55	798.29	43.69	25.64	28.66	0.352	0.434	0.214	0.91	0.73	0.91	0.81	0.73	0.81	-0.345	-0.194	-0
11	28	7.08	11.46	4.9	37.07	22.91	40.7	0.89	0.79	0.83	0.919	724.4	768.52	39.29	28.97	32.3	0.362	0.432	0.206	0.91	0.73	0.91	0.81	0.73	0.81	-0.349	-0.187	-0
12	29	8.98	13.54	5.56	36.74	24.18	44.08	0.89	0.79	0.83	0.918	902.42	960.67	39.07	30.74	34.82	0.365	0.433	0.202	0.91	0.72	0.91	0.8	0.72	0.8	-0.351	-0.184	-0
13	30	7	13	6	43.79	24.14	40.13	0.89	0.79	0.83	0.92	861.17	909.84	46.23	30.48	31.66	0.356	0.436	0.209	0.91	0.73	0.91	0.81	0.73	0.81	-0.348	-0.189	-0
14	31	6.72	14.84	7.98	51.67	24.61	36.17	0.9	0.79	0.83	0.922	1001.05	1046.72	53.99	30.8	28.42	0.347	0.437	0.217	0.91	0.73	0.91	0.82	0.73	0.82	-0.343	-0.196	-0
15	32	5.56	14.14	5.78	54.38	22.89	42.14	0.89	0.79	0.83	0.917	869.62	927.91	57.97	29.18	33.38	0.347	0.445	0.208	0.91	0.72	0.91	0.81	0.72	0.81	-0.347	-0.188	-0
16	33	6.7	13.96	4.32	47.47	23.71	54.2	0.89	0.79	0.83	0.911	883.23	962.23	51.68	30.88	42.79	0.36	0.448	0.192	0.91	0.7	0.91	0.8	0.7	0.8	-0.355	-0.175	-0
17	34	5.76	11.48	7.96	57.21	30.02	35.26	0.9	0.79	0.83	0.925	954.88	981.1	58.75	37.15	27.15	0.345	0.435	0.22	0.91	0.73	0.91	0.82	0.73	0.82	-0.342	-0.198	-0
18	35	6.1	13.32	6.1	56.52	27.32	45.05	0.89	0.79	0.83	0.917	983.43	1042.24	59.84	34.77	35.09	0.35	0.444	0.205	0.91	0.72	0.91	0.81	0.72	0.81	-0.348	-0.186	-0
19	36	5.72	12.36	6.6	59.96	29.35	42.5	0.89	0.79	0.83	0.92	986.21	1033.74	62.8	37.03	32.85	0.347	0.443	0.21	0.91	0.72	0.91	0.81	0.72	0.81	-0.346	-0.19	-0
20	37	8.58	13.12	4.46	46.42	30.54	62.95	0.89	0.79	0.83	0.912	1079.75	1171.22	50.31	39.89	48.47	0.369	0.447	0.185	0.91	0.7	0.91	0.79	0.7	0.79	-0.359	-0.168	-0
21	38	5.82	11.9	5.94	60.76	31.27	47.42	0.89	0.79	0.83	0.918	1007.36	1062.05	64.01	39.75	36.44	0.351	0.445	0.204	0.91	0.71	0.91	0.81	0.71	0.81	-0.349	-0.185	-0
22	39	7.84	11.18	6.96	53.87	38.02	47.34	0.89	0.79	0.83	0.921	1176.89	1220.4	55.83	47.77	35.72	0.359	0.438	0.204	0.91	0.72	0.91	0.81	0.72	0.81	-0.35	-0.185	-0
23	40	5.44	13.72	5.74	69.42	29.82	52.28	0.89	0.79	0.83	0.914	1086.87	1162.48	74.18	38.43	40.37	0.347	0.454	0.199	0.91	0.71	0.91	0.81	0.71	0.81	-0.351	-0.18	-0
24	41	8.34	13.52	4.26	52.79	33.18	71.94	0.89	0.79	0.83	0.909	1195.32	1307.31	57.7	43.83	54.82	0.368	0.453	0.179	0.92	0.69	0.92	0.79	0.69	0.79	-0.362	-0.162	-0
25	42	6.58	13.34	5.46	64.62	33.61	59.15	0.89	0.79	0.83	0.913	1196.47	1282.94	69.23	43.56	45.12	0.355	0.453	0.192	0.91	0.7	0.91	0.8	0.7	0.8	-0.354	-0.174	-0
26	43	8.62	11.14	5.38	53.77	41.44	62.45	0.89	0.79	0.83	0.915	1261.14	1335.26	56.88	53.31	46.68	0.367	0.445	0.188	0.91	0.7	0.91	0.79	0.7	0.79	-0.357	-0.171	-0
27	44	7.06	11.84	4.22	59.57	36.56	71.09	0.89	0.79	0.83	0.91	1153.47	1251.44	64.6	48.05	53.68	0.364	0.455	0.181	0.92	0.69	0.92	0.79	0.69	0.79	-0.36	-0.164	-0
28	45	5.66	14.64	4.16	73.81	31.09	73.7	0.89	0.79	0.83	0.906	1179.58	1303.75	81.57	41.45	56.54	0.354	0.465	0.18	0.92	0.68	0.92	0.8	0.68	0.8	-0.359	-0.163	-0
29	46	7.3	14.58	5.2	68.79	36.38	70.75	0.89	0.79	0.83	0.909	1400.46	1520.84	74.66	47.86	53.45	0.358	0.459	0.183	0.91	0.69	0.91	0.79	0.69	0.79	-0.359	-0.166	-0
30	47	6.1	11.18	5.24	71.18	40.72	62.97	0.89	0.79	0.83	0.914	1219.47	1296.14	75.59	52.62	47.09	0.356	0.454	0.19	0.91	0.7	0.91	0.8	0.7	0.8	-0.355	-0.173	-0
31	48	8.12	12.48	7.78	70.36	47.09	57.14	0.89	0.79	0.83	0.918	1603.57	1666.11	73.05	59.72	42.11	0.356	0.447	0.197	0.91	0.71	0.91	0.8	0.71	0.8	-0.353	-0.179	-0
AVE:	33	6.67	12.93	5.75	52.68	33.93	35.55	0.89	0.79	0.83	0.918	925.41	983.76	52.68	33.93	35.55	0.355	0.44	0.206	0.91	0.72	0.91	0.81	0.72	0.81	-0.349	-0.186	-0

Mathematical Notes

1. The Translog Cost Function:

2. The Factor Share Functions:

∂ln(C)/∂ln(wL) = (∂ln(C)/∂wL )/ (∂ln(wL)/∂wL) = (1 / C(q;wL,wK,wM)) * ∂ln(C)/∂wL * wL = wL * L(q; wL, wK, wM) / C(q;wL,wK,wM) = sL(q;wL,wK,wM),

∂ln(C)/∂ln(wK) = (∂ln(C)/∂wK )/ (∂ln(wK)/∂wK) = (1 / C(q;wL,wK,wM)) * ∂ln(C)/∂wK * wK = wK * K(q; wL, wK, wM) / C(q;wL,wK,wM) = sK(q;wL,wK,wM),

∂ln(C)/∂ln(wM) = (∂ln(C)/∂wM )/ (∂ln(wM)/∂wM) = (1 / C(q;wL,wK,wM)) * ∂ln(C)/∂wM * wM = wM * M(q; wL, wK, wM) / C(q;wL,wK,wM) = sM(q;wL,wK,wM).

3. The Factor Demand Functions:

L(q;wL,wK,wM) = sL(q;wL,wK,wM) * C(q;wL,wK,wM) / wL,

K(q;wL,wK,wM) = sK(q;wL,wK,wM) * C(q;wL,wK,wM) / wK,

M(q;wL,wK,wM) = sM(q;wL,wK,wM) * C(q;wL,wK,wM) / wM.

4. The Factor Demand Elasticities:

C = wL * L / sL = wK * K / sK = wM * M / sM, → sL = (wL * L) * sK / (wK * K) = wL * L / C,

∂L/∂wL = [(∂sL/∂wL * C + sL * ∂C/∂wL) * wL - (sL * C)(1)] / wL^{^2} = [(dLL/wL * wL*L/sL + sL * L) * wL - (sL * wL * L/sL)] / wL^{^2} = (L /wL) * (dLL/sL + sL - 1), so
ε_L,L = ∂ln(L)/∂ln(wL) = ∂ln(L)/∂wL * ∂wL/∂ln(wL) = ∂L/∂wL * wL/L = (- 1 + sL + dLL/sL).

∂L/∂wK = [(∂sL/∂wK * C + sL * ∂C/∂wK] / wL = [dLK/wK * (wL *L / sL) + ((wL * L) * sK / (wK * K))*K] / wL = [dLK*L/(wK*sL) + L*sK/wK], so
ε_L,K = ∂ln(L)/∂ln(wK) = ∂ln(L)/∂wK * ∂wK/∂ln(wK) = ∂L/∂wK * wK/L = (sK + dLK/sL).

∂L/∂q = [(∂sL/∂q * C + sL * ∂C/∂q] / wL = [(dLq/q)*(wL*L/sL) + (wL*L/C)*C*(∂ln(C)/∂q)]/wL, so
ε_L,q = ∂ln(L)/∂ln(q) = ∂ln(L)/∂q * ∂q/∂ln(q) = (∂L/∂q)*(q/L) = q * ∂ln(C)/∂q + dLq / sL,

5. Cost Function C(q;wL,wK,wM) Concave in Factor Prices:

∂ln(C)/∂ln(wL) = sL = wL * L / C = wL * ∂C/∂wL / C → ∂C/∂wL = sL * C / wL,

∂²ln(C)/∂ln(wL)∂ln(wL) = [(∂wL/∂ln(wL) * ∂C/∂wL + wL * ∂²C/∂wL∂ln(wL)) * C - wL * ∂C/∂wL * ∂C/∂ln(wL)] / C²
= [(wL * ∂C/∂wL + wL * ∂²C/∂wL∂wL * wL) * C - wL * ∂C/∂wL * ∂C/∂wL * wL] / C²
= wL * ∂C/∂wL / C - wL * ∂C/∂wL * wL * ∂C/∂wL / C² + wL * wL * ∂²C/∂wL∂wL / C
= sL - sL * sL + wL * wL * ∂²C/∂wL∂wL / C = dLL, so

wL * wL * ∂²C/∂wL∂wL / C = dLL - sL + sL * sL

∂²ln(C)/∂ln(wL)∂ln(wK) = [(∂wL/∂ln(wK) * L + wL * ∂L/∂ln(wK)) * C - wL * L * ∂C/∂ln(wK)] / C²
= [(0 + wL * ∂²C/∂wL∂wK * wK) * C - wL * L * ∂C/∂wK * wK] / C²
= - wL * L * wK * K / C² + wL * wK * ∂²C/∂wL∂wK / C
= - sL * sK + wL * wK * ∂²C/∂wL∂wK / C = dLK, so

wL * wK * ∂²C/∂wL∂wK / C = dLK + sL * sK