There was very potent weed in the 70s, but there was a lot of lower potency weed too. Most people smoked seedy, lower potency Mexican, rolled into pencil-thick joints and passed around. Smoking 2-3 joints at a sitting among a group of 4 or 5 people was ordinary. By seedy I mean 10-20 seeds in a medium sized joint’s worth of weed. Anybody who’s smoked seeded weed knows its far less potent that sinsemilla from the same plant.
In addition to the seeds, the Mexican being mostly sativa, meant wispy small buds that didn’t lend themselves to trimming - and certainly the Mexicans, who saw seeds as a way to bulk up the weight of their priced-by-the-kilo commodity weed, weren’t going to waste time trimming down buds for the Yanquis…
But there were beautiful Colombian Golds and Reds, Panama Red, Acapulco Gold and other primo strains available for the lucky few with good connections. I remember a bag of “British Honduran” (Belize for young’ns) that was just psychedelic, no other word for it. Oh to have saved just a couple of those seeds as they rolled down the spine of my favorite de-seeding album, a worn copy of the Airplane’s “Blows Against the Empire” (it included a production credit for a guy whose role was “snowman” hehe.)
Indica hybrids and sinsemilla technique changed everything. Buds got fatter and denser, and being seedless, meant more room for trichomes per volume of bud. Big fat seedless buds fetched a premium - 2 or 3x seedy Mex, so close trimming became the fashion to show off this new premium product. Around 1980 or so a friend of mine brought back an oz of “California sins” to our East Coast crew, and proceeded to snip off little bud bits with nail scissors to place into bowls for us. We’d never seen bud treated so daintily.
By '82-'85 US-grown sinse ruled the market, and those Central and South American sativas just weren’t around much anymore. Nixon’s war on drugs, especially the Paraquat program, where the DEA paid Mexican police to spray pot fields with a Vietnam War-era defoliant that was poisonous to consume, helped rid the US of evil Mexi commersh as well.
Also gone was the “soaring sativa high” that even the commercial Mex could deliver, with enough puffing on the laughing bones. That loss was not immediately appreciated, the heavy indica stone just seemed so potent so who cared? Besides, we had cocaine to keep the party going. LOTS of cocaine 
…
Is today’s pot more potent than 70s pot? As sold to the consumer, measured by volume, I’d have to say generally, yes. But it has as much to do with growing, harvesting and trimming technique as anything, plus the heavy stoniness of the indica’s cannabinoid mix. That’s why old farts like me are constantly looking for that sativa buzz of yore.
If only the war on drugs hadn’t focused on Mexican cannabis, and Central and South Americans had developed a sinsemilla culture sooner, and the Hippy Trail led down the spine of the Sierra Madre instead of through the Rif and Hindu Kush ranges, we might be tripping on psychedelic American sinse sativas instead of nodding off on couch-lock kushes today.
-b420
in the 80’s. We were smoking homegrown blonde afghani that would turn people green.