Short form, 100% count- exact counts
STF1 - all persons & by race - Hispanic Origin
A - States - BlockGroups
B - Blocks
C - Nation, MSA, cross-state geographies
D - Congressional District
STF2 - 34 race and Hispanic Origin groups
A - Hierarchy within states to tracts
B - States to areas 1,000 or more
C - Nation to areas of 10,000 or more
D - Congressional District
Long form, sample coverage - estimates
STF3- all persons & by race - Hispanic Origin
A - States - BlockGroups
B - Zip Codes
C - Nation, MSA, to areas of 10,000+
D - Congressional District
STF4 - 34 race and Hispanic Origin groups
A - States to tracts
B - Hierarchy in state to areas 2,500+
C - Nation to counties
The design of the 1990 PUMS files is similar to that of 2000, so refer to Microdata Overview for an explanation, while relying on the links the next section of this page to obtain the data.