For nearly 18 months now, Tucsonans have been told our metropolitan area has topped 1 million population, but then March 20, the U.S. Census Bureau released its latest statistics reporting the population for all of Pima County was 967,089 as of July 2007.

So is metro Tucson’s population over 1 million or not?

Yes, it is over 1 million - in fact it’s 1,003,235, according to the Arizona Department of Economic Security (DES).

David Taylor, technical services coordinator for Pima Association of Governments (PAG), says the difference between the two comes down to how each does the estimating.

The Census Bureau uses administrative records such as birth certificates, school enrollments, driver’s licenses and death certificates to come up with its estimates. Taylor and other state officials use housing permits and housing data to calculate their estimates.

So who is right?

Taylor says it’s anyone’s guess until the next full-blown census is taken in 2010 but, historically, the DES estimates have proven to come closer. He says the Census Bureau’s estimates tend to be more on target in the first few years after a census but then become progressively less accurate toward the end of each decade.

According to a comparison done by Jeff Romine, senior regional economist with the Maricopa Association of Governments, the Census Bureau comes closest to matching the state’s estimates in Maricopa County where the two are less than one percentage point apart - the Census Bureau says the county’s population is just under 3.9 million versus the state’s figure of just over 3.9 million.