Breaking news: Millennials are getting older. And as they enter the next stage of life — marriage, kids, higher salaries —Gen Y is beginning its exodus from busy cities, just like the generations that came before it.Data released by the U.S. Census Bureau earlier this week show that some 27,000 millennials between the ages of 25 and 39 left big cities like New York, San Francisco and Houston in 2018 for greener, and less expensive, pastures, the Wall Street Journal reports. Chicago, Las Vegas, Washington, D.C. and Portland, Oregon, are also seeing large numbers of residents leave.That marks the fourth year in a row that there has a noticeable decline in the millennial populations in major cities.And where are they moving? To combat the ever-increasing housing costs and lack of access to family-friendly amenities, to nearby suburbs, mostly, Axios reports. But the Journal notes other, more affordable, metropolitan areas are also gaining millennials, including cities like Austin, Columbus, Ohio, Los Angeles, San Diego and Seattle.A 2018 report from SmartAsset revealed similar results. Using 2016 Census migration data, SmartAsset compared the number of people aged 20 to 34 who moved to over 200 U.S. cities to the number who moved away from them. It found that the most popular cities for millennials to move to include Seattle, Denver and Minneapolis — not New York or San Francisco.Notably, workers early in their career who are younger than millennials are still moving to big cities to find career opportunities.A 2018 survey of 1,200 adults aged 20-36 from Ernst & Young also revealed that more millennials are buying homes in the suburbs than in cities. Much of that is likely to do with the price: A 2018 report from Zillow found that home buyers will pay 26.5% of their income each month for a median-value home in a city, compared to 20.2% for a similar home in the suburbs.”It was a surprise to me to see this generation increasingly choosing suburban locations to buy homes,” Cathy Koch, EY’s Americas tax policy leader, told CNBC Make It. But “the ‘suburbs’ may very well be smaller cities close to larger urban areas — these still afford the richness of city living (including employment opportunities) at maybe lower home prices.”As more millennials buy houses, that trend will likely continue.Don’t miss: Almost 70% of millennials regret buying their homes. Here’s whyLike this story? Subscribe to CNBC Make It on YouTube!