It is important to note that the average effective marginal tax rates faced in the actual
population will tend to be below those found in sample family analyses. This happens
for a variety of reasons. Families do not tend to participate in all of the programs for
which they are eligible, not all families are eligible for transfer programs (because
of immigrant status, for example), and many families will retain eligibility for some
benefits in many months, even though they increase work. Results also vary for those
who work in some months and not others.