Conversely to what we explored with the ACS, the varying recall interval in the NHIS creates a possibility that as the survey year progresses, respondents might give responses influenced by their current incomes. If respondents were reporting their prior calendar year incomes as requested, then we would expect to see fairly uniform distributions of income over the survey year, although population change might influence the pattern to some degree. Even though respondents are being asked to report their incomes for the same period, the composition of the population is not constant over time, and families change as well. We saw earlier that with a growing lag between the end of the income reference year and the measurement of family composition, the estimated poverty rate increased. This would apply to the NHIS income measures in a way that it does not apply to the ACS, and in so doing it might obscure any evidence that respondents later in the year were reporting more income than respondents earlier in the year.
The distribution of family income in the NHIS by calendar quarter shows no evidence of change over time (Table V.12). For the reasons discussed above, we find this inconclusive with respect to respondents’ compliance with the task of reporting their family incomes for the previous calendar year, as there may be confounding factors. If there is any influence of current income on reported income, however, it would have to be small.
We do find a statistically significant increase between the first and fourth quarters in the proportion of family income allocated, which grows from 29.9 percent to 31.9 percent (Table V.13). This could suggest that respondents are having more difficulty reporting their prior calendar year incomes as the recall interval increases. But the increased non-response is very modest and does not suggest that respondents in the fourth quarter are having a serious problem with the reporting of their income for the prior calendar year or that the quality of the data may be compromised.
|Family Income ($)||Percent Distribution by Interview Quarter|
|0 - 4999||3.10||3.24||3.44||4.03|
|5000 - 9999||4.64||4.86||4.40||4.72|
|75000 and over||28.13||28.31||28.07||27.75|
Source: Mathematica Policy Research, from tabulations of calendar year 2002 income from the 2003 NHIS.
|Family Income Allocation||Percent Distribution by Interview Quarter|
Source: Mathematica Policy Research, from the 2003 NHIS.