Nielsen Media Research is considering recalculating some of its local market audience estimates to account for people displaced by Hurricane Katrina. Normally, the universe estimates wouldn’t be updated until next summer. The current 2006 estimates will be effective Sept. 24, the start of the traditional TV season.

How viewership information is handled could have a million-dollar impact on stations in affected markets including New Orleans, Houston and Baton Rouge, La.

With the city of New Orleans evacuated, no ratings are coming from the No. 43 television market. Kerry Kielar, director of marketing communications for Nielsen Media Research, said last week that Nielsen had no idea when it would be able to release data from that designated market area, which had 672,150 television homes representing 0.61 percent of the U.S., according to local market universe estimates released last month by the ratings service.

Many of the evacuees are at least temporarily resettled and probably are already watching television in other markets, notably Houston and Baton Rouge. But at this point, viewing by those estimated half-million people-who will be buying new cars, food and other consumer products-will show up in ratings only in those rare cases in which evacuees happen to be staying with families who are already members of the Nielsen sample. Their viewing would be registered as guests in diaries filled out by the host families.

Nielsen normally does not measure out-of-home viewing, whether it’s in second homes, bars or offices. Nor does it plan to measure viewing in churches or shelters.

In order to reflect new viewing patterns that might emerge when the post-Katrina situation settles, Nielsen might take the unusual step of adjusting its universe estimates in markets where the population has undergone a sudden shift, Ms. Kielar said.

Nielsen bases its universe estimates on data from the U.S. Census Bureau and from research company Claritas. Nielsen uses its data on television penetration to produce its universe estimates.

Ms. Kielar said the company will work with state and local officials on updated estimates. “I think we’re learning along with everyone else,” she said.

In the latest market ratings, Houston moved up to No. 10 from No. 11, with 1.938 million homes. Baton Rouge is DMA No. 96, with 305,000 TV households.

In New Orleans, Nielsen said, fewer than 100 of the 350 set-top meters are reporting. Ratings won’t be reported until there are enough to create a statistically sound sample from all of the parishes, Ms. Kielar said.

“We’ll have to wait,” she said. “There are still people who have no homes and no electricity. Getting back online [with Nielsen] is not a major priority for them.”