Those percentages don't mean much out of context. Was the curriculum less stringent back then (I.e. graduating people that shouldn't have been able to)?
Unfortunately, that context (a survey of the difficulty of curriculums for CS programs across the country, per graduation class) would be very hard to collect.
However, we could try to look at CS school drop-out rates, and how many students picked-up or dropped the CS major. Nevertheless, it would be hard to separate "difficult courses" from "students who don't really love CS" as boit and pnathan suggested.
However, we could try to look at CS school drop-out rates, and how many students picked-up or dropped the CS major. Nevertheless, it would be hard to separate "difficult courses" from "students who don't really love CS" as boit and pnathan suggested.