Millennials are playing homeownership catch-up.

First-time buyers rushed into the market last year, making 38% of all single-family home purchases, the biggest share since 2000, data released Thursday by Genworth Mortgage Insurance show. The 2.07 million new or existing homes bought by first-timers was 7% more than in 2016, according to the insurer, part of Genworth Financial Inc.

Millennials, who were putting off purchases because of student-debt burdens and a preference for renting, are becoming a force in the market as the oldest of the group get married and have children, said Tian Liu, chief economist for the insurer. At the same time, older homeowners are choosing to stay and upgrade their current properties instead of trading up, he said.