My grandfather used to say that people will keep moving here as long as it is a better place to live than Toledo, Ohio. He died in the early 1970s, when Sarasota and Manatee counties had about 220,000 residents. I wish I could tell him how right he was. The population has tripled since he died, and last year 102 more people moved here from Toledo.

The last 15 years have been so good for the Sarasota-Bradenton metropolitan area (Sarasota and Manatee counties) that many people have forgotten that the economy they depend on is strange and fickle. In 2006, 6,788 babies were born and 8,327 people died in the metro, a net loss of 1,539 residents. That is strange. The only reason the local economy kept growing is because 13,174 more people moved here than moved away, according to the Census Bureau. About 80 percent of those in-migrants came from another state, and most of them came to retire. That is even stranger.

Fewer than one-fifth of Americans in their 50s say they will even consider moving across state lines when they retire. The few who actually do it are not normal; they are lucky enough to afford such luxuries, and footloose enough to cut all ties to their hometowns in exchange for lots of sunshine. According to the IRS, residents of our metro had an aggregate household income of $15.5 billion at the beginning of 2006. During the year, the net gain in aggregate income caused by people moving here from other states increased that sum by perhaps $350 million.

And that’s the fickle part. Every year a tide of new money washes over our economy and makes jobs grow. Everything is great as long as that happens, and it has been happening steadily for quite a while. But a national recession can destroy Sarasota and Manatee’s economy as quickly and suddenly as a hurricane. The metro’s population has increased by about 40 percent since the last true bust in 1991, so many readers of Biz941 have never seen the bottom drop out. But our economy depends on in-migration and as long as that is true, things will get tough as soon as snowbirds get scarce.

Florida’s current epidemic of housing foreclosures could be the opening act of the next bust. But so far, it looks more like the end of a sprint. Everyone knows that the state had the third-highest foreclosure rate in the United States in October 2007, and that Atlas Van Lines is moving more families out of Florida than it is moving in. But local population growth has not stopped: Sarasota County’s population increased 2.1 percent from 2006 to 2007, and Manatee County’s population increased 2.6 percent, according to the University of Florida’s Bureau of Economic and Business Research. Tourists are still spending, so maybe we’ll escape a full-blown recession. But we are vulnerable, because any market that depends on discretionary spending can turn on a dime.

In most American metros, more people are born every year than die, and most jobs do not depend on visitors and newcomers. Nationally, the median age is about 36; in Sarasota County, it is almost 50. Still, things here aren’t really that weird. Affluent retirees may give the metro its image and fertilize its economy, but only about one-quarter of local residents are aged 65 or older. Most of the metro’s 703,000 residents are of working age, and 18 percent are children. The truth is that each neighborhood in Sarasota, Bradenton and Venice is inhabited by different kinds of people, who coexist peacefully as long as the annual flood of money shows up. Some of the places in our metro are a lot like normal American towns. Others are among the most demographically extreme spots in the United States.

Retirement Royalty

Consider Longboat Key. If you divide the life cycle into thirds and count up the people in each category, you’ll find that most places in the United States and Florida have more young people (under age 35) than they do middle-aged people (aged 35 to 64), and more middle-aged people than they do old people (aged 65 and older; see chart 1). This rule applies to the three parts of our metro where working people can find affordable housing: Palmetto, Bradenton and North Port. But in Longboat Key, there are 20 residents aged 65 and older for every resident under age 35. The national pattern is also reversed in Englewood, Venice and the unincorporated eastern part of Sarasota County. In all four of these places, the dominant age group is 65-plus, and children are relatively hard to find.