It’s a billion-dollar business — and then some.

In 2016, Colorado’s dispensaries bagged $1.3 billion in recreational and medical cannabis sales, based on Colorado Department of Revenue tax data released Thursday.

To put the state’s third year of regulated recreational marijuana sales in perspective, Year One totaled $699.2 million (combined with medical sales) and Year Two jumped up to $996.2 million. The trend should continue in Year Four, but beyond that? It’s a murkier proposition.

“Colorado has had a really good run, being the first mover,” said Miles Light, an economist with the Marijuana Policy Group, which provides economic and market consulting services to legal cannabis markets. “Now, as other states legalize, some of these external benefits that are occurring are going to be eroded.”

Light noted that in 2017, none of the eight states that voted to legalize the medical or recreational use of marijuana will have implemented their regulations.

Related: How will California spend $1 billion in pot tax revenue?

2016 was the year in which the $100-million-month became a baseline and heralded a record-breaking summer: The combined sales for July, August and September were $376.6 million.

Monthly sales topped $100 million in eight of the 12 months. In December, which is typically a strong month for cannabis transactions, pot shops’ sales were a little more than $114.7 million, a 13 percent increase from the $101.3 million recorded in December 2015.

In this file photo, Rachel Schaefer, of Denver, smokes marijuana on the official opening night of Club 64, a marijuana-specific social club. (AP Photo/Brennan Linsley, File)

Colorado’s third year of legal recreational marijuana sales also saw some external pressures, notably in the form of price drops on wholesale cannabis.

“It was a difficult year,” said Sally Vander Veer, president of Medicine Man, an operator of one of Denver’s larger medical and retail dispensaries.

“We’re still seeing a steady increase in the number of customers and patients, but (sales) numbers are pretty flat,” she said.

The Colorado Department of Revenue’s tax data don’t provide information about transactions, so it’s difficult to know the impact of price declines on the overall sales totals. The data do show that recreational marijuana accounted for an $875 million share of that haul while medical sales accounted for roughly $438 million.

They also show that Colorado brought in about $199 million in tax and fees revenue for the calendar year. Marijuana tax revenue is put toward areas such as school construction projects, public health and law enforcement.

It’s the visitor demand that drives a lot of this incremental growth in Colorado’s marijuana industry, Light said. That includes the tourist who buys an eighth for a ski trip here and that’s also the visitors who come into the state to purchase product to illegally supply to other markets, he said.

The Denver Post reported in January that research commissioned by the Colorado Tourism Office found interest in legal weed waning among visitors. “2016 represented a return to the more usual Colorado traveler,” tourism director Cathy Ritter said.