The 1995/1996 Household Income, Expenditure - (PDF, 101 mb ...

11.11
results over time. Females consume more than expected. The intercept is
smaller, indicating the decline in budget shares of food and beverages over
time. In general, the coefficient values, model fit, and importance of the
variables are quite good, pointing to the robustness of the equivalence scale
models. The use of a standard equivalence scale would not be appropriate.
More will be said about the use of the equivalence scales in the Appendix to
the next chapter, but for now it is enough to suggest that any critical
household estimate might be adjusted to account for household size, sex and
age characteristics using the predictive coefficients.
Another adjustment which really must be made to economic estimates
over time is deflating to control for general price increases. It is standard
practice to deflate prices by some index of the cost of living, and usually the
Consumer Price Index (CPI) serves this function well enough. In Egypt's
case, however, the CPI is measured with so much error that "adjustment" of
level data merely serves to confound the bias inherent in the statistic itself
(CPI measurement error is the subject of Chapter V). Still, some adjustment
must be made, and in the absence of an alternative measure of cost of living
increases, the official CPI produced by CAPMAS must be used. Table II.10
sets out a comparison of expenditures, incomes, and wages from two periods,
adjusted and not adjusted by household equivalence, the official all items CPI,
and thi food only CPL Means are presented by SAS-generated standard
errors, as well as medians. The official CPI index used is March, 1996, the
midpoint of data collection for the 1995/1996 HIECS. Here it is appropriate to
explain the existence of two income estimates from the old data. The CAPMAS
publication estimates from the 1990/1991 HIECS were from the NEWINC.SD2 data
set, produced by an incorrect and non-complete household-level merge of
individual number codes with the individual number codes of a separate
income source questionnaire. The INDV.SD2 income estimates are based on the
merging of individual-level demographic codes and their income sources,
summed by household.
The median value of an estimate - half of households have a value less
than the median, the other half have a value greater than the median - is a
better statistic than the mean for capturing the idea of relativeness. It is
much better when the median rises than when the mean rises. Based on the
assumptions, the conclusions about median estimates follow from Table 11.10:
6 The fact that the standard errors are created by SAS and therefore
generated under the assumption of a simple random sample design should not
detract from their usefulness in making asymptotic inferences. In many cases
the standard errors can be inflated by a factor of the design effect shown for
the statistic in previous tables.