Moving vans and cars with license plates from other states are everywhere, and that isn’t a fluke. Colorado is full of people on the move.

More than one in 10 Colorado households that filed a tax return in 2014 lived in another county or state the year before. That’s more than in any other state.

Nationally, 6.4 percent of 2014 tax returns listed an address in a different county or state the year before, according to tax return data from the Internal Revenue Service.

If Colorado is a migration destination, then Denver serves as its Ellis Island, claiming nearly one in five of the households making a major move within or to the state.

“Denver is a gateway. People know the name Denver. They don’t know the name Aurora,” state demographer Elizabeth Garner said.

Among other highlights gleaned from the returns:

• The entire metro area, including Boulder, claimed nearly two-thirds of households moving to or relocating across county lines within Colorado.

• About 54 percent of people on the move were Colorado residents who crossed county lines, while 46 percent were out-of-staters.

• Former Californians filed the most Colorado tax returns, followed by people from Texas, Florida, Illinois and Arizona.

• Migration is an ebb and flow. Texas was the top destination for those leaving Colorado, followed by California, Florida, Arizona and Washington.

• After netting things out, Illinois lost the most households to Colorado, followed by California and New York, according to the tax returns.

Meeting in the middle

Jeff and Lauren Griffith had lived the California dream, first in Los Angeles, where they went to college, and then in a San Diego condo, where they moved after their first child, Luke, arrived. A second child, Emma, set them on the hunt for more room.

“We wanted a house with a swing set in the backyard and a garden, and we weren’t going to be able to afford that in San Diego,” said Lauren, 37, who grew up north of Chicago.

Around Christmas in 2014, they moved to Erie, where they rented a house with a yard for less than what their San Diego condo cost.

“If we could have made it work, we would have,” Lauren said. “It was hard, really hard.”

Their migration story goes beyond a search for more affordable real estate. Lauren’s brother Graham Haas moved to Colorado from Illinois in 1999, drawn by his love of skiing. He fell in love and settled down in Erie with his wife, Mandy, and their kids.

Mike Haas, Lauren Griffith , Luke Griffith, Sandy Haas, Emma Griffith and Jeff Griffith near the Griffith home on April 6, 2016 in Erie, Colorado. The

Mike Haas, Lauren Griffith , Luke Griffith, Sandy Haas, Emma Griffith and Jeff Griffith near the Griffith home on April 6, 2016 in Erie, Colorado. The Griffiths moved to Colorado from San Diego, to get closer to Lauren’s brother and parents, Sandy and Mike Haas, in the winter of 2014. (Brent Lewis, The Denver Post)

Lauren and Graham’s parents, Sandy and Michael Haas, lived their whole lives near Chicago, as had three generations of the family before them. But the chance to watch their grandchildren grow up persuaded Sandy and Michael to make the move to Erie in summer 2012.

“We really never thought we would leave after generations and generations in Illinois,” said Sandy, who lived in Antioch, Ill., a village surrounded by lakes 50 miles north of Chicago.

“We didn’t hesitate,” she said.

After a century in the same area, Erie was where one branch of the Haas family of Antioch, Ill., chose to reassemble itself.

Millennial magnet

As a group, households that moved to Colorado were smaller and had lower average adjusted gross income per return — $52,340 — than those who stay put — $76,481 per return.

The reason: Young adults are more migratory than other age groups, and because they are just starting their careers, they earn less.

“This age group moves a lot, especially 18- to 29-year-olds, and they move for all sorts of reasons,” said Jeffrey Arnett, a research professor in the psychology department at Clark University in Massachusetts.

Millennials are waiting longer than previous generations to start careers, get married and settle down, said Arnett, who studies “emerging” adults. With fewer ties, they are freer to move.

Emma Griffith, 3, smiles at her mother, Lauren while they play a game with her brother Luke 7, in the backyard while having a snack at their home on April

Emma Griffith, 3, smiles at her mother, Lauren while they play a game with her brother Luke 7, in the backyard while having a snack at their home on April 13, 2016 in Erie, Colorado. The Griffiths moved from San Diego, California to Colorado late 2014 to be closer to Lauren’s brother and her parents, who relocated from Chicago. (Brent Lewis, The Denver Post)

Arnett was a consultant on the Mayflower Mover Insights study, which tried to peel back what is important to young adults when it comes to relocating.

Denver ranked third among the cities that Mayflower’s millennial customers moved to last year after Dallas and Chicago. Other popular destinations for young adults were Seattle; Atlanta; Los Angeles; Portland, Ore.; Charlotte, N.C.; and Washington, D.C.

Nearly half of the 18- to 35-year-olds that Mayflower surveyed said they would move either to be near a romantic partner or to find one. Love was second only to work as a draw. And nearly 60 percent cited a preference for living in a city center or inner suburb. More than half said good restaurants are a must.

Millennials like to live in areas where other millennials are flocking, and they use social media to share their experiences, which has helped create migration magnets, Arnett said.

“It takes on a certain momentum of its own,” he said. “Once a lot of them are going to a city like Denver, it does gain a self-perpetua ting quality.”

Arnett admits he doesn’t fully understand the appeal of Denver compared with places like Boston and San Francisco. Ten or 20 years ago, young adults didn’t list Denver as an exciting place to live — and now they do.

Migration patterns

Migrants to Colorado show wide variations in their income depending on where they come from. Transplants from New Hampshire and the District of Columbia, while fewer in number, earn $116,571 and $112,427, which is the highest adjusted gross incomes of any group migrating to Colorado.

At the other end of the scale are transplants from Nevada, who make $25,042 in adjusted gross income, less than half the average for all migrants moving into Colorado. The predominance of lower-paying jobs in hospitality and food service in Nevada might explain some of the gap, said Garner, the state demographer. Other states whose migrants have the lowest income included Maine, Mississippi, Vermont and South Dakota.

Lawrence Yun, chief economist with the National Association of Realtors, said that high living costs in California’s Bay Area and Silicon Valley are pushing workers to other metros like Denver, and they are bringing a higher earning potential with them.

Although 2015 tax returns aren’t available, estimates from the U.S. Census Bureau show the migration wave into Colorado has only accelerated. One question about all the newcomers is: How long will they stay put?

Sandy Haas said although she and her husband miss family and longtime friends, they have no regrets about moving to Erie and won’t be returning to Illinois.

Calls on Skype and holiday visits can’t compare to ferrying their grandchildren to practices and watching them grow up, she said. And views of the snowy mountains help when she feels nostalgic about the lakes she left behind.

Longish winters aside, Lauren Griffith said she and her family also don’t regret the move to family-friend Erie. They plan to buy a house with a driveway facing south, not north.

Then there are the rainbows. Until he moved to Colorado, 7-year-old Luke had seen only one rainbow, Griffith said. Last summer, he counted 40.

Aldo Svaldi: 303-954-1410, or @aldosvaldi