An area can be considered an MSA if it has one or more cities of at least 50,000 residents, with social & economic integration of the cities with surrounding rural areas. There were 332 MSAs (including 5 in Puerto Rico), for the 1990 census.

Census results are published in the Decennial Census of the United States about 2 years after the census is taken. Lots of census information is summarized annually in the Statistical Abstract of the United States.

More than 4/5s of the world’s population is counted in some kind of census.