Each year, millions of Americans and their families pick up and move. Some may go all the way across the country, but most typically migrate shorter distances within the same regions.

Research suggests that housing is the main reason why nearly half all Americans move. Indeed, it's typical to see residents relocating from counties with high real estate costs to nearby ones with less expensive housing. Family considerations account for 30 percent of relocations, while about another 20 percent move primarily for career opportunities, according to the U.S. Census Bureau.

Migration data released by the Internal Revenue Service (IRS) earlier this month provides an updated snapshot of the communities where people are moving to and from. We’ve compiled data showing net migration flows between all counties from 2014 to 2015.

Four of the top 10 biggest recent net migration flows originated from Los Angeles County, Calif. That’s in large part due to the fact that it’s the nation’s most populous county with more than 10 million residents. In all, L.A. County lost a net total of about 40,000 residents to other parts of the country between 2014 and 2015.

We've highlighted the top county-to-county net migration flows, summarized below, using exemptions claimed on tax returns to approximate persons moving.

Net Migration: 11,047

Los Angeles County to San Bernardino County, Calif.

Southern California recorded the nation's top net migration flow. The IRS data suggest more than 30,000 people moved east to San Bernardino County, while slightly more than 19,000 relocated in the opposite direction to Los Angeles County. Like other common migration patterns, it's largely a result of people seeking less expensive housing with more space.

Migration from San Bernardino County to L.A. County has remained fairly steady in recent years, although total numbers of individuals moving in either direction have declined.

Net Migration: 7,140

Miami-Dade County to Broward County, Fla.

For years, movement north into Broward County has consistently been among the top migration flows. Broward County recently welcomed more than 23,000 taxpayers from Miami-Dade County for a net gain of 7,140.

Broward, which includes Fort Lauderdale and a few other cities along the coast, is mostly suburban. It’s likely that many of its new residents are recent immigrants; Miami is an immigration hub where immigrants initially settle before relocating.

It’s worth noting that the influx of residents from Miami-Dade to Broward has slowed somewhat, though. Net migration had topped 10,000 each year before the most recent 2014-2015 period.

Net Migration: 6,684

Queens to Nassau County, N.Y.

More than 13,000 people moved to Nassau County from Queens, while only about half as many moved in the opposite direction. Like other jurisdictions in and around New York City, immigrants from abroad largely offset Nassau County's domestic migration losses, so it continues to record population increases.

Net Migration: 6,031

Harris County to Fort Bend County, Texas

Fort Bend County has emerged as one of the nation’s fastest-growing counties in recent years. But of all its new residents, the majority arrive from neighboring Harris County, which includes Houston.

State Demographer Lloyd Potter attributes part of the migration pattern to the downturn in Houston’s energy sector. The other part is that younger couples are forming families and moving out in search of more affordable housing. “The whole area has been growing with newer housing stock and nice subdivisions,” he says.

The approximately 22,600 people who moved from Harris County to Fort Bend County represents a slight decline from recent years.

Net Migration: 5,813

Brooklyn to Queens, N.Y.

Nearly 20,000 people moved from Brooklyn to neighboring Queens, with a net migration of 5,813. This migration flow has historically been among the most common moves within New York.

That said, more people overall move out of Queens than move in from other parts of the country. But the borough’s total population continues to tick upward thanks to international migration. 

Net Migration: 5,518

Los Angeles County to Riverside County, Calif.

Nearly 16,000 people moved from Los Angeles County to Riverside County, with a net migration of 5,518. Riverside County typically experiences a net migration gain among residents moving within California, while losing more people to other states.

Net Migration: 4,970

Los Angeles County to Clark County, Nev.

The vast majority of Clark County’s new residents arrive from out of state. Many relocate from California, where the cost of living is much higher. The IRS figures suggest numbers of newcomers to the county from other parts of the country have climbed in recent years.

Migration to Clark County from Los Angeles Counts accounted for, by far, the single largest county-to-county flow across any state border. The next-largest took place in Miami-Dade County, where a net total of 1,803 people moved from Harris County.

Top Net Migration Per Population

Other Top Net Migration Flows:

Los Angeles County, to Orange County, Calif: 4,827 Manhattan to Brooklyn, N.Y.: 4,746 Manhattan to Bronx County, N.Y.: 4,355 Another way to assess migration between counties is to compute approximate migration per total population. By this measure, the largest numbers of residents relocated from the following counties given the total exemptions claimed (excluding smaller migration flows not exceeding 1,000):

San Juan County, N.M., to McKinley County, N.M.: 2,994* Christian County, Ky., to Montgomery County, Tenn.: 1,074 City of St. Louis, Mo., to St. Louis County, Mo.: 2,213 City of Baltimore, Md., to Baltimore County, Md.: 2,989 San Francisco County, Calif., to Alameda County, Calif.: 2,876 Suffolk County, Mass., to Norfolk County, Mass.: 2,077 New York County, N.Y., to Kings County, N.Y.: 4,746 Hudson County, N.J., to Bergen County, N.J.: 1,955 Fairfax County, Va., to Loudoun County, Va.: 3,605 New York County, N.Y., to Bronx County, N.Y.: 4,355 *These counties cover tribal lands, so changes to mailing addresses are likely responsible.

View updated migration data for all U.S. counties