Trophy assets in bustling U.S. markets have become an increasingly hot commodity as investment in the office sector surges nationwide.

Office sales grew 69% nationwide over the last four quarters compared to the year prior, according to a new report from Avison Young. Of the $40.8B worth of offices that changed hands, 71% were trophy or Class-A spaces.

Much of that activity came in the fourth quarter, which had more than $15B of transactions, up from about $8B in Q4 2023.

The increase in sales has been especially sharp in the California markets.

Los Angeles and San Francisco saw $3.5B and $1.7B of sales, respectively, in the last four quarters, which represented increases of 147% and 140% from the prior year.

Secondary office markets in the Golden State also got a big boost. Office sales in San Diego skyrocketed 563% to $730M, while the East Bay saw its transaction volume grow 372% to $1.6B.

Trophy assets accounted for 35.3% of U.S. office transactions in the first half, up from 22.7% for all of last year and 21.4% in prepandemic 2019.

Class-A properties have continued to constitute the majority of sales in the sector, but their share is waning. Those buildings accounted for 42.7% of sales so far this year, down from 47.7% in 2024 and 54% in 2019.

This year's acquisitions have been driven by private investors, which accounted for 57% of all buyers, up from 54% last year. The share of international buyers dropped from 8% last year to 6% this year, the lowest in the last decade.

International investors have been offloading U.S. office assets. They made up 15% of all sellers, up from 10% last year.