By Caroline Fairchild – The Huffington Post

U.S. legal marijuana sales are projected to hit $1.5 billion this year, and that could look like nothing in just a few years.

Data from Medical Marijuana Business Daily shows that total sales could quadruple to $6 billion by 2018 on the back of legalization efforts in Washington and Colorado, as well as the growing medical marijuana industry.

The two states both legalized the recreational use of weed in November. Elsewhere, 18 states and Washington, D.C. have made medical marijuana legal, while 10 othershave formal measures pending to legalize medical marijuana, according to the National Cannabis Industry Association.

That’s reflective of a wider acceptance of the drug. A recent Pew Research Center poll discovered a majority of Americans support pot legalization for the first time in more than four decades. As many as 52 percent of Americans support legalizing weed — 45 percent do not — and nearly three-fourths say the amount of money spent enforcing marijuana usage laws is not worth the cost.

Such growing support has led marijuana-tied businesses to pitch their companies to Wall Street investors, the Los Angeles Times reported in March. Take Vincent Mehdizadeh, founder of MedBox, an automated weed dispensing machine company. He’s seeking $20 million from investors in anticipation of potential expansion.

“Everybody’s loosening up a lot because they realize the momentum has shifted and the financial world is going to have to make room for this industry,” Mehdizadeh told the LAT. “Wall Street and investment banks are going to have to come along for the ride, eventually.”

Thinking about investing in the marijuana industry yourself? Be sure to keep the risks in mind. It was reported last year that 500 of the estimated 3,000 U.S. marijuana dispensaries either had been closed by the government or shut down in the past year.