Oregon is fortunate that people from other states continue to move here. It helps expand our intellectual capital, our workforce and out tax base, among other benefits. In-migration has also added to a tight housing market—but new census data compiled by the Oregon Office of Economic Analysis show that tightness could be a lot worse.

Over the past 15 years, however, the percentage of people who live with their parents or share homes with roommates is way up.

"Young adults are living at home longer, or living with roommates to a larger degree than a decade ago, let alone two decades ago," writes Josh Lehner, a state economist in a new analysis of census data.

"Within the Portland region this decline means there are nearly 28,000 fewer households today among the 25-44 year age group than there would be if household formation rates were the same as back in the mid-2000s. Across all age groups, the decline in household formation rates in the Portland region results in 36,000 fewer households on net. This is equal to 3 years of new construction, which is a massive number."

Here's a chart Lehner together that shows the decline in "headship," i.e. the formation of new households by people who become the "heads" of those households.