Invariably some sampled households do not participate in surveys
because they refuse to do so or because nobody is at home during the
interview visit. This is referred to as “unit nonresponse” and is distinct
from “item nonresponse,” which occurs when some of the sampled
respondents participate but refuse to answer certain questions, such
as those pertaining to income or consumption. To the extent that
survey nonresponse is random, there is no concern regarding biases
in survey-based inferences; the sample will still be representative
Poverty rates
About the data
Economy States and markets Global links Back World Development Indicators 2014 25
of the population. However, households with different income might
not be equally likely to respond. Richer households may be less likely
to participate because of the high opportunity cost of their time or
concerns about intrusion in their affairs. It is conceivable that the
poorest can likewise be underrepresented; some are homeless or
nomadic and hard to reach in standard household survey designs, and
some may be physically or socially isolated and thus less likely to be
interviewed. This can bias both poverty and inequality measurement
if not corrected for (Korinek, Mistiaen, and Ravallion 2007).