75%. And I actually tried the 24h game marathon before, but do full meal breaks count or do I have to snack from the sofa? If the latter, then I failed. If not, my full Metal Gear Solid trilogy pack marathon went better than expected. I played them in story order, so in my sleep-deprived state MGS2 made me REALLY paranoid.
Also, I think the reason people can die from this isn't the lack of sleep but the lack of regular food and water. I stayed up about 96 hours once. Once again the deprivation made me a panicky nutcase, but I was nowhere near death.