For an illegal, expensive, and according to many people immoral, practice, I'd say >10% is widespread, yes.
Dunno if legality even has much an impact. Many things are a lot less illegal in some places, you know, without dramatic increases in use. Expensive, like, for high performers? Are we talking again of the college students, hung over and sleep deprived due to partying all night, taking stimulants?
“It cannot be gotten for gold, neither shall silver be weighed for the price thereof. / It cannot be valued with the gold of Ophir, with the precious onyx, nor the sapphire. / The gold and the crystal cannot equal it: and the exchange of it shall not be for vessels of fine gold. / No mention shall be made of coral, or of pearls: for the price of wisdom is above rubies.”
Another 477 days are past, so what have I been up to? In roughly topical & chronological order, here are some major additions to
gwern.net:Statistics:
QS:
Black-markets:
Bitcoin:
Tech:
Literature/fiction
Sand, on:
compiled & expanded anthology of my poems
Misc:
Site:
I began A/B testing my site design to try to improve readability:
I began a newsletter/mailing-list; the back-issues are online: