The strongest strain of marijuana is Bruce Banner #3 at 28% THC. So how does that compare to grass in the bad old Greatful Dead, Chech and Chong days?

Recently scientists discovered (not surprisingly) that from 1993-2008, THC concentration gradually increased, according to a 2010 paper in the Journal of Forensic Sciences. While researchers are confident that potency is always increasing, they also concede limitations in their methods to uncover data: “The change in cannabis potency over the past 40 years has been the subject of much debate and controversy… The [Potency Monitoring] program has strived to answer this cannabis potency question, while realizing that the data collected in this and other programs have some scientific and statistical shortcomings.”

For one thing, there’s a lot more bud being dissected and tested now than ever before. In the 70s, government scientists analyzed 3-18 seizures a year. By the new millennium they were looking at over 1,000 seizures.

So it’s not entirely possible to track potency over the years, and it’s also uncertain what the future of flower potency will look like. There may be a limit to how much THC genetics are capable of packing into a bud. “Anyone getting a reading over 25, it’s really hard to do,” said Gennifer Murray of CannLabs. “And then it doesn’t necessarily mean you’re going to quote-unquote get higher. There’s a lot of things that go into the plant—over 500 constituents of the plant that play into this.”