*Notes:*

Summary File 3 is a sample (a subset of a population) survey enumerating approximately one in six households. Numbers are then adjusted to "estimate" the population based on the sample.
On the other hand, Summary File 1 enumerates 100-percent of the population, so "Percent of the population in sample" table in SF3 shows the quality of the SF3 sample compared to the 100% count.