Data center inventory in top U.S. markets jumped 33% from a year ago, even as vacancy hit an all-time low, illustrating the hard-charging demand that's showing no signs of slowing down.

CBRE, the world's largest commercial real estate services and investment firm, published a new report on global data center trends, showing supply reached 16 gigawatts in the first quarter of the year across the world's 16 largest data center markets, a 25% annual increase. Despite the growing capacity, global data center vacancy dropped from 8.3% to 6.7%.

Vacancy is even lower in American data center hubs: 0.3% in Northern Virginia, 1% in Atlanta, 1.8% in Dallas-Fort Worth and 2.2% in Chicago. Vacancy dropped in all four top U.S. data center markets.

Pat Lynch, the executive managing director for CBRE's Data Center Solutions, said data center developers are in "catch-up mode," with new capacity getting scooped up before it even hits the market. Companies are signing leases for facilities that won't be delivered for three to four years. Eighty percent of space under construction in top American markets has been preleased. "I think the stats kind of speak for themselves," Lynch said. "So, while we're producing record inventory, it's getting taken up just as quickly."

The U.S. has 3,000 operational data centers, with another 1,500 or so in various stages of development, according to a recent Pew Research Center report. Lynch said counting data centers is difficult, because definitions vary. A recent report for Congress noted that data centers vary in size and scope, "ranging from closets, to larger rooms within a single enterprise, to dedicated standalone structures serving the needs of multiple customers or tenants, known as colocation."

Data centers are in high demand, driven by needs in artificial intelligence, cloud computing and more. Power availability is a key bottleneck for data center growth, but Lynch said community resistance is also a challenge to delivering on the demand. "There's a lot of good things that come from data centers that we candidly have not talked about and promoted as much as we should have," Lynch said.

Northern Virginia remains the world's data center leader. The region got an early foothold in the data center market and never looked back, and it's now expanding from Ashburn in Loudoun County, Virginia, north to Maryland and south to Richmond. "It has so many unique characteristics that have developed over time, when you think about undersea cables that have come into that area, and then the emergence of some of the large cloud hubs for some of the Fortune 10 companies that really started, because you had capacity and a lot of corporate data centers, a lot of colocation sites there," Lynch said. "So, it's a market that has built upon itself and continues to do so. And so, you've got so much existing infrastructure that is nearly impossible to replicate elsewhere."

Atlanta has seen massive growth, building as a possible alternative to Northern Virginia going forward. By the first quarter, Chicago replaced Phoenix in the top four U.S. data center markets. Dallas-Fort Worth jumped two spots to become the nation's third-largest data center market. Tennessee and West Texas are emerging markets.