Cocaine really wasn't THAT big in the '70s. It wasn't until the late '70s and into the '80s when it was affordable and available enough for regular people beyond the rich and famous.
Statistically speaking (and in my classes we've looked at this quite a bit) its hands down pharmaceuticals and if you had to narrow it from there, opioids. In a lot of areas in the US more high schoolers have tried a pharmaceutical than marijuana and if it hasn't yet surpassed it nationwide, its certainly close or approaching. This would include benzos, amps and opioids (among some other less common options, not JUST opioids).
If you look at trends throughout US history, they've found that about every 10 years the abuse landscape shifts and it goes from a more stimulating drug to a more sedating drug and back. With meth booming in the '90s and even cocaine having somewhat of a resurgence, for years they were predicting heroin to make a big come back in early 2000's... they missed the mark, but not by far. Same basic chemistry except the drugs that exploded come in vacuum-sealed bottles instead of small stamped baggies.
