Huge jumps in daytime populations aren't just a big city phenomenon. It happens in a number of places, according to first-ever estimates from the Census Bureau.

In Tysons Corner, Va., where relatively few people actually live but thousands earn their livings, the daytime population swells by 292 percent on weekdays, Census says. In El Segundo, Calif., the daytime count jumps 288 percent.

Of course, everything is relative, for Tysons Corner and El Segundo are considered "small" places. It's the big places like New York City and Washington, D.C., which see the biggest daytime gain in pure numbers.

The Big Apple has the largest estimated daytime population of any U.S. city, at more than 8.5 million persons. But that's only half-a-million more than the city's nighttime population, which, at 8 million, is bigger than that found in any other area. And as a result, the 7 percent increase puts New York in the middle of the pack on percentage change among cities with more than a million residents.

It also becomes somewhat more crowded in Washington, D.C., which has the second highest numeric daytime population. Some 410,000 workers boost the capital city's population by 72 percent during normal business hours.

D.C. is one of the four cities with 100,000 more night denizens which show the highest percentage gains from 9 a.m. to 5 p.m. The other three of Irvine, Calif., Salt Lake City and Orlando.

And speaking of Orlando, one of the most extreme examples of daytime population increases -- not just on weekdays but seven days a week -- occurs in a little town called Lake Buena Vista. This is the home of Disneyworld, which has almost no permanent residents but swells to an employment center of more than 30,000 people during the day.

Other big cities with large daytime gains are Atlanta (62 percent), Tampa (48 percent) and Pittsburgh and Boston (both around 41 percent).

Again, though, the places where the largest percent increases in daytime over nighttime populations occur tend to be those with small resident populations. Typical examples of sizable expansion of daytime populations in small cities can be found in places such as Paramus, N.J.; Redmond, Wash.; and Beverly Hills, Calif., among others.

These findings come from the first-ever U.S. Census Bureau estimates of the daytime population for all counties and more than 6,400 places across the country, based on Census 2000 data. "Information on the expansion or contraction experienced by different communities between nighttime and daytime is important for many planning purposes, including those dealing with transportation and disaster relief operations," says Census Bureau Director Louis Kincannon.

"By providing information on the number of people not living in the area, but nevertheless greatly affected by the event, the data can provide a clearer picture of the effects of disasters such as Hurricanes Katrina and Rita."

About 250,000 people worked in New Orleans prior to Katrina. Almost 150,000 of these workers were residents of New Orleans, but the remaining 100,000 lived outside the city.