The Federal Aviation Administration has for years predicted steady growth in the commercial drone industry, but the latest data shows officials drastically underestimated just how much the tech would take off.

Last year alone, commercial drone operators registered more than 175,000 new aircraft with the FAA, increasing the total number of commercial drones in use across the U.S. by more than 170 percent, according to the administration’s annual aerospace forecast. The surge in registrations, which expanded the commercial drone market to 277,000 units, “far exceed[ed]” the 44 percent growth officials predicted at the beginning of the year.

The disparity was so substantial that officials significantly revised their previous estimates for the industry’s long-term growth.

Last year, the administration predicted there would be roughly 452,000 commercial drones in use by 2022, but now it expects the industry to hit that size around the beginning of next year. Based on the latest data, FAA predicts the commercial drone market will triple over the next five years, hitting 835,000 aircraft by 2023.

“The significant growth in this sector over the past year demonstrates the uncertainty and potential of the market,” officials wrote in the report. “We anticipate the growth rate of the sector will slow down over time—nevertheless, the sector will be much larger than what we understood as recently as last year.”

The commercial drone industry’s rapid growth has largely been driven by advancements in “consumer-grade” drones, or units priced below $10,000, the report said. These aircraft today account for about 95 percent of the total commercial drone market, but as the industry consolidates, the FAA predicts this figure will drop to roughly 85 percent by 2023.

Commercial drones, which are used for research, pilot training, filming, building inspection and a slew of other professional activities, are typically more expensive and robust than the model aircraft used by hobbyists, but recreational drones are far more numerous, according to the FAA. Today, officials estimate there are roughly 1.25 million amateur drones in use across the country, and they expect the market to grow to 1.4 million by 2023.

In the report, the administration also released the latest stats for the Low Altitude Authorization and Notification Capability program, which make it easier for pilots to get approved to fly in urban areas and controlled airspace. Since the program launched last year, the administration issued more than 55,000 authorizations.

The agency also said it had certified some 116,000 drone pilots through the end of 2018. As recreational and commercial drones become more popular in the years ahead, officials expect the total number of certified pilots to hit 350,000 by 2023.