The ETFMG Alternative Harvest exchange-traded fund said Wednesday it passed $1 billion in assets under management on Feb. 4, making it the biggest cannabis ETF in the world and the only one listed in the U.S. The ETF is now tracking the performance of a basket of 38 cannabis stocks, including Canada's Cronos Group Inc. and Canopy Growth Corp. , two players viewed as promising because of large investments from established companies. The fund has gained 37% in the year to date, bolstered by outsize gains by Cronos, up 95%, and Canopy, up 70%. Canada fully legalized cannabis for adult recreational use last October, and a handful of Canadian companies have now listed in the U.S. "This milestone validates investor interest in this emerging industry as well as investor sentiment toward a decades-old drug policy," said Kris Monaco, managing partner of Level ETF Ventures, an index provider to the fund. The Horizons Marijuana Life Sciences ETF , which trades in Canada, was down 5.5% on Wednesday, but has gained 42% in the year to date. The S&P 500 and the Dow Jones Industrial Average have gained about 9% in the year so far.