# Cobb Douglas Essay

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• Published : November 26, 2012

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Empirical Methods of Economics

1) In the Cobb-Douglas production function, the relation between output, Q, labour input, L, and capital, K, is specified as follows:

Q = 〈L ®1K®2

a) Specify the econometric model. Explain how you arrive at the model you specify.

This model is purely deterministic. We do not expect real economies subject to myriad perturbations (or even just rounding errors in the reported data) to strictly adhere to this model, so we need an error term, μ, Ε(μ)’0. We might try Q = 〈L ®1K®2+μ, but then Q(L = 0) = Q(K = 0) =µ, implying that output could be negative (Q < 0) under realistic inputs (L = 0 or K = 0). Because output cannot be negative, we use: [pic]

b) Rewrite the model in (a) in a form suitable for estimation by OLS. [pic]

c) Assuming constant returns to scale obtain the labour intensive and capital intensive form of the model in (b) Constant returns to scale is a condition under which scaling the inputs by a factor (λ) scales the outputs by the same factor. Using the OLS form of the equation and imposing this condition, we obtain an equivalent result to that of the textbook (Gujarati, 2003): [pic]

d) Using the data in Table 1, estimate the models in (b) and (c) using Eviews. e) Report the results of your estimations.

[pic]

[pic]

f) Using t- and F tests what can you conclude from the estimated model.

The F-test tells us that both models fit the data better than would be expected by chance (P < 1e-13). The high R2 for a large number of data points (relative to the degrees of freedom) also suggested this result. Next we use the R2 of each model, along with 8.7.10 from our book to assess the probability that the restricted model is just as good as the unrestricted model on this dataset (Gujarati, 2003), at a significance level of P = 0.05, (for which the critical value will be F = 4.3, since df in the numerator is 1, and the denominator is 22). In the...