Don't look now Buffalo, but Rochester is gaining on you.
The population of the Buffalo Niagara region has shrunk this past decade to the point that the Rochester region is nearly as big, according to the latest census estimates released Tuesday.
The Buffalo Niagara region, comprising Erie and Niagara counties, ranks as the 50th largest region in the nation.
The Rochester region, which covers five counties, ranks 51st.
"Wow, that really changes my perspective," said Kathryn A. Foster, director of the University at Buffalo Regional Institute. "If you look 50 years ago, it wouldn't have been close."
Buffalo Niagara's population is estimated at 1.12 million, compared with 1.03 million for metro Rochester -- a difference of more than 88,000 people.
It's not that the Rochester region is gaining in population, Foster explained. It's just losing people a lot more slowly than the Buffalo region.
Rochester has lost 0.2 percent of its population since 2000, when it ranked as the 49th largest metro, while the Buffalo region, the 42nd largest metro 10 years ago, lost 4 percent.
"We're both losing population and losing rank," Foster said. "But Buffalo is losing at a faster pace than Rochester."
The population estimates shouldn't be confused with figures from the 2010 census, which is just under way.
The Census Bureau does an official head count every 10 years. But it annually estimates state, county and city populations by adjusting the most recent census numbers using birth, death and migration information, plus data from tax returns.
The latest state and county estimates show that Buffalo Niagara had another difficult decade:
*The Buffalo region lost more than 46,000 people between 2000 and 2009. Only the metro areas of Detroit, Cleveland, Pittsburgh and hurricane-ravaged New Orleans saw larger declines.
*Ninety percent of the Buffalo region's population loss came from Erie County. No other county in the state lost more people.
*Surrounding counties suffered during the decade, too. The population went down 5.1 percent in Cattaraugus County; 4.8 percent in Orleans County; 4.7 percent in Wyoming County; 4.5 percent in Chautauqua County; and 1.5 percent in Allegany County.
Foster cautioned that these figures are just estimates and sees them as an opportunity to remind people about the importance of filling out the 2010 census form.
Still, there's no denying the downward trend.
"This was a tough decade," Foster said. "It was not as tough as the '70s, but it was a tough decade in the sense we experienced a couple of recessions in the beginning and the end."
But there is a hint of hope in the figures.
Estimates show that the population losses the past two years in Buffalo Niagara have slowed considerably since the middle part of the decade.
The region lost just 250 people between July 1, 2008, and the same date in 2009, according to estimates.
Much of that had to do with small gains in Niagara County.
Some have speculated that the migration patterns have changed for the better in the state in the past couple of years, because of the cooling of the job and housing markets across the rest of the country.
Others, like County Executive Chris Collins, believe that the numbers support their belief that the worst is over for Buffalo Niagara and that the region's population has bottomed out.
"Many parts of our community are experiencing a renaissance of sorts," Collins said. "As a result, we are on our way back to building some of the population losses we have suffered over the past 25 years."
It's hard to tell by the estimates, Foster said.
"I'd hate to make too much of a one-year change," she said, "but you can make the argument that the losses have slowed. There's less volatility."
"We may see the decade ahead look different," she added. "No one knows what will happen."
The U.S. Census Bureau estimated that 19.5 million people lived in New York on July 1, 2009, up more than a half-million since the last official count in 2000.
New York City accounted for most of that growth -- 383,195 people -- though Long Island and suburban Hudson Valley counties also grew in the last decade.
New York City's growth has been helped by thriving immigrant communities. Fast-growing mid-Hudson Valley areas like Orange County benefited from house hunters priced out of more expensive areas closer to the city.
The story was different in many upstate areas, which have been losing population for decades as people, especially young college graduates, leave for the South and West.
The Census Bureau reports that rural counties suffered the greatest population losses. Topping the list was northern New York's Hamilton County, which lost 8.4 percent of its population since 2000; Delaware County, which lost 5.3 percent; and Cattaraugus County, which lost 5.1 percent.
The Associated Press contributed to this report.