It's going to be different for everyone depending on several factors. That is why you can test at several durations and the various power profile such as sprinter, pursuit, and time trial. Also note that CP for shorter durations is going to be higher than longer durations. One "standard" is that FTP (60) is roughly 95% of 20 minutes, BUT someone with a higher anaerobic capacity will be able to produce more power over 20 minutes for the same FTP, and therefore FTP would be a lower percentage.