The Current Population Survey (CPS) questionnaire is more detailed than the American Housing Survey (AHS) instrument, especially regarding non-wage income: it asks about receipt and amounts of 19 types of non-wage income for each person, while the AHS questionnaire asks about receipt of 9 categories of non-wage income, and a total amount for each family.

Average household income in 1999 is 9 percent lower in the AHS than in the CPS; family earnings are almost the same; and non-wage income is 32 percent lower. The discrepancy has become worse over time, especially since 1995.

The problem is more due to the failure of many respondents to report any non-wage income, than to wrong amounts being reported. Underreporting of non-wage income increases with the number of adults in the household, suggesting that the CPS's practice of asking about each person makes a difference. This finding is confirmed by logit analysis that holds demographic background characteristics constant. The largest potential sources of underreported non-wage income are interest, dividends, social security and pensions,