America will have 2.5 million drones by the end of this year and the number will increase to seven million by 2020, the Federal Aviation Administration (FAA) said in a report release Thursday. While the number of hobby drones is expected to reach from 1.9 million in 2016 to 4.3 million by 2020, commercial drones will see a four times rise from 600,000 to 2.7 million in 4 years.

“Unmanned aircraft systems will be the most dynamic growth sector within aviation,” the agency said in the report. But it also added that future security and regulatory measures by the U.S. government will be deciding factor on the way civilian drone market grows.

In December, the FAA brought in set of rules which stated that registration of small unmanned aircraft weighing more than 0.55 pounds and less than 55 pounds, including payloads such as on-board cameras, was necessary.

However, the FAA stated that predictions for commercial drones are difficult to establish because of the dynamic, quickly-evolving nature of the market.

“Both sales and fleet size estimates share certain broad assumptions about operating limitations for small UAS [unmanned aircraft systems] during the next five years: daytime operations, within visual line of sight, and a single pilot operating only one small UAS at a time,” FAA said.

The FAA is expected to publish final regulations about drone use within the next few months. An estimated 90 percent of the drone fleet in 2020 will reportedly cost an average of $2,500, while the higher-end models are likely to touch $40,000 mark.