Poverty measures in Panama are based on consumption. Given that the Panama CCT program supposes a monetary benefit, to estimate the `contrafactual’ or `post-transfer’ consumption distribution, it is necessary to know the effect caused by the increase in the household income into its consumption.
To this aim, we estimate the total household consumption as a function of its income. An easy way to compute this relation is to assume a constant marginal propensity along the entire income distribution79. This idea can be resumed in the following equation:
(4)
where and means the total household consumption and income respectively, represents the vector of observed characteristics that affects the consumption, represents the vector of non observed characteristics (errors) and is the marginal propensity to consume.
It is known that in equation (4) the income might be correlated with the error term (if the error term contains omitted variables that are correlated with the variables included, if contains measurement errors, or if are determined jointly with). This causes inconsistent OLS estimation.
To go beyond this problem, we also propose to estimate equation 4 using the method of Instrumental Variables (IV). This technique is the standard prescription for correcting such cases and it gives:
(5)
where is called the instrument for and it have the following two properties: (i) it is correlated with , , and (ii) it is uncorrelated with , .
Following Deaton (1997), we used as instrumental variable the average income of the village where the household is placed estimated without the income of the household (expresses in log.). Hence, z is determinate by the following expression:
con h = 1,…,75 (7)
Where the subindex i means household, the subindex h means the village where the household is placed and, Nh means the household population of each village.
Table A.3.6.1 shows four specifications using both IV and OLS methods. Model 1 is the simplest specification where total consumption (in log.) is estimated as a function of its total income (in log) and the household size. Model 2 adds regional controls. Model 3 included controls for demographics characteristics. Finally, model 4 incorporates educational controls.
Performing a Hausman test we confirm that the OLS estimation results to be inconsistent under these models (Table A.3.6.2). As we mention before, the income coefficient denotes the marginal propensity to consume. This coefficient results to be statically significant in all IV models. Moreover, these estimations show that the value of the marginal propensity in Panama is between [0.7460, 0.8243].80
Table A.3.6.1: Estimation of the Marginal Propensity to Consume
|
|
Source: Own estimation based on ENV 2003 data.
Note: OLS means Ordinay Least Square estimation, IV means Instrumental Variables estimation
|
Table A.3.6.2: Hausman Test
|
|
Source: Own estimation based on ENV 2003 data.
|
Dostları ilə paylaş: |