If you’ve ever smoked up with someone who lived through the 1960s, you may have heard them remark that marijuana is much stronger than it used to be.

But is that actually true, or just a hippie myth? Here’s the straight dope.

How we measure marijuana strength

Because it’s too difficult to ask Willie Nelson, we’re forced to measure weed’s potency the only way we really can: by examining its concentration of THC, or tetrahydrocannabinol, the psychoactive chemical that gets us high.

More specifically, we can weigh THC content of a given cannabis strain against its level of CBD (or cannabidiol), as this chemical seems to counteract some of THC’s most pronounced effects. Marijuana can also be lab-tested for various other compounds, both beneficial and undesirable. But in general, the simplest way of understanding weed’s potency is by analyzing its THC content.

How strong is weed today?