Based on 2000 census figures, states that were able to add congressional seats had a significant advantage in immigrant populations over states like Mississippi that lost seats.

"The states with the largest populations and contingents of representatives also had the largest immigrant communities and continuing influxes of immigrants," said Karen Woodrow-Lafield, a Mississippi State sociologist.

She is among several professionals advising the United States Census Bureau on underestimated immigration and evaluation of the 1990-2000 population change. Since 1984, she has completed extensive studies using federal Immigration and Naturalization Service data.

Though few state residents may remember, Mississippi in 1940 had more residents than Florida, Woodrow-Lafield said. "By contrast, the next Congress will include 25 representatives from Florida and only four from Mississippi," she said.

The effects unauthorized residents and other categories of immigrants might have had on the 2000 census apportionments were among her most recent study areas. Among the findings:

--To have kept five congressional seats, the Magnolia State needed an additional 35,764 persons counted in the census, assuming all other state counts stayed the same.

--In addition to natural increase and internal migration, immigration was a major factor in the states' gains and losses.

Woodrow-Lafield said federal statistical systems do a poor job of tracking new residents with temporary visas, asylum status or many new, alternative statuses.

As a result, there are few effective ways to keep up with those either overstaying their time limits or violating the terms of their temporary admissions. Assuming a higher overall population of immigrants, her recent research model showed apportionment numbers changing either negatively or positively for California, New York, Michigan, Mississippi, Pennsylvania, and Wisconsin.

Woodrow-Lafield said more than 567,000 students arrived from abroad in 1999 to study in the U.S., bringing 36,641 spouses and children. Most enrolled at universities and colleges; only about 2 percent were admitted for vocational education.

In addition to students, more than 457,000 aliens arrived as temporary workers, along with 109,681 spouses and children.

While her work with other demographers and Census Bureau officials probably will improve official numbers for some states, Mississippi is unlikely to be among them.