About 6% of Americans move into a different county each year, according to Census Bureau data released this year. And while that may not sound like a lot, it represents nearly 17 million people who are packing their bags in search of better jobs, cheaper living or just a new life. What’s more, experts think more and more people will do this as the economy improves—and it’s starting to happen already: While the moving rates hit an all-time low between 2009 and 2010, they ticked up slightly between 2012 and 2013.

Millennials—those born between the years 1977 to 1992—are the most likely group to move (roughly one in five do)—and that’s especially true if they live in certain types of places, according to a new analysis by real-estate firm RealtyTrac. In general, millennials are moving away from counties with smaller populations (average population of 178,277) and to counties with larger populations (average population of 587,522), the report revealed. That’s likely because they’re trying to get out of areas with fewer and low-paying jobs, explains Daren Blomquist, vice president of RealtyTrac.

Millennials on the move are heading to or near big cities, likely because those tend to have robust job markets. Arlington County and Alexandria City, near Washington, D.C., and Orleans Parish, near New Orleans, are the counties with the fastest growing populations of millennials. They’re followed by counties in San Francisco, Denver and New York, among others. “The millennial generation is generally moving from lower-priced to higher-priced markets for both buying and renting, with the tradeoff being more jobs (lower unemployment) and higher median incomes in the markets they are moving to,” the report revealed. Blomquist adds that, in general, millennials are more likely to move into more walkable urban areas of a city than to the outskirts.

Boomers, on the other hand—folks born between the years 1945 to 1964—are acting in the opposite way. They’re moving from higher-priced to lower-priced markets and from counties with larger populations to those with smaller populations. Blomquist says this is likely because many are retiring or gearing up for retirement, and thus are less concerned with the job market and more concerned with affordable living.

While areas in or near big cities like San Francisco and New York are attracting millennials, boomers are flocking to warmer weather and smaller towns. The areas with the highest percentage change in boomers since 2007 include counties in Florida near Punta Gorda, Orlando and Cape Coral, as well as counties near Prescott and Phoeniz, Ariz., and Hilton Head, South Carolina.