In terms of demographic trends, Northwest Indiana is a tale of two counties.
Last year, Porter County ranked 10th statewide in population growth, while Lake County lost more residents than every other county in Indiana.
Lake County had the biggest population decline out of Indiana's 92 counties in 2013, losing 1,662 residents, according to U.S. Census Bureau figures analyzed by the Indiana Business Research Center at Indiana University's Kelley School of Business.
Porter County gained 876 residents, growing at a rate of 0.53 percent.
The population changes were not as dramatic on a percentage basis. Lake County lost four times more residents than the county with the second-biggest drop in population but ranked 25th worst statewide in percent of decrease -- shrinking by 0.34 percent.
"My suspicion is that the stark decline over the last few years is that fewer people are moving into Lake County from Illinois," state demographer Matt Kinghorn said.
Porter County was the 24th fastest-growing county in the state if measured by percent of growth instead of the sheer number of new residents.
Population changes in LaPorte, Newton and Jasper County were minor, all at 0.16 percent or lower, near the middle of the pack statewide.
Lake County remained Indiana's second most populous county with 491,456 residents. Porter County kept its position as ninth-largest with a population of 166,557 residents.
Last year's changes reflected long-term trends. Lake County had an estimated 513,269 residents in 1960, while Porter County's population soared by more than 170 percent over the last 54 years, according to U.S. Census data.
During the 2000s, Lake County started to grow again, adding an average of 1,147 residents a year, Kinghorn said. An Indiana Business Research Center study found more than 50 percent of its new residents came from Illinois between 2001 and 2008.
But the migration, mostly from Cook County, slowed down after the economic downturn, when people were less likely to get married, start families and move to outlying areas like Lake County, Kinghorn said.
Lake County had the highest net outflow in Indiana last year with a net loss of 2,840 residents moving elsewhere, which was partly offset by 1,375 natural births.
Lake County is no longer attracting enough residents to offset natural losses of residents moving away to college, retiring to warmer climates or to taking jobs elsewhere, Kinghorn said. Not enough people – especially not enough younger families – are moving in to maintain the population.
Since 2010, Lake County has lost an average of about 1,500 residents a year.
"It's enough to get your attention after the growth that went on over the previous decade," he said. "It's a strong reversal of fortune."
Statewide, Indiana's population grew by a rate of 0.51 percent last year, up from 0.33 percent in 2012.
"There's slow improvement in the economy and the housing markets," Kinghorn said. "As we get back to full speed, the typical levels or movement and migration will occur. But household formations and other key indicators have remained slower than they were before the recession."