Thanks to the rise of e-commerce, the value of big-box warehouses now surpasses that of office buildings.

A new report by Colliers International shows large high-tech warehouses of more than 200K SF with 28-foot ceilings have become particularly valuable.

The brokerage tracked big-box industrial performance in 14 markets in North America and found these assets now command a record-low 5.8% cap rate, down from nearly 8.5% in 2009.

Lower cap rates are favorable because they indicate an asset is of greater value. Office cap rates dropped to 6.7% in U.S. suburban and rural markets in 2017 and stood at 5.7% in urban markets, Bloomberg reports.

Amazon has been a major driver for the sector and occupies 102M SF of warehouse space across nearly 260 facilities. The e-commerce behemoth intends to add another 37.8M SF before the end of 2018. Companies such as Blackstone Group are also providing a boost to the sector. The asset manager has been on an industrial real estate shopping spree, acquiring a 41-property industrial portfolio for $359M this week. In December, Blackstone bought a 22M SF, $1.8B portfolio and in February the firm purchased a 1.71M SF portfolio for $151M.

Vacancy rates in the sector have hit all-time lows, even with an influx of construction. Markets such as Indianapolis, Phoenix and California's Inland Empire ranked among the top markets for warehouse demand, Bloomberg reports.