Chester uses the fry scream technique which doesn't hurt your throat at all, yet he still avoids screaming at a concert as much as possible and doesn't use much power as he used to back in the days. That's because it affects his pitch, it makes it harder for him to hit high notes. A very good example is in this performance of Given Up at 11:38 http://www.youtube.com/watch?v=4Cldm2d5LNs He can still scream like back in 2003/2004 as much as he wants, but choses not to, because he couldn't perform the majority of songs from MTM and ATS.
What John said. Chester hasn't lost his screaming voice at all. He can still switch it on and do it whenever he wants, he just chooses not to do it as much anymore because he wants to preserve his voice/pitch over the traditional 90 minute live show. Especially when they usually do shows within a day or two of eachother back to back. His vocals are fine. If anything they've gotten better with age.
Mmm. . . Slight difference. I have noticed recently it sounds like he's really clinching his throat. It's almost like a nasaly sound. Listen when he tries to annunciate. He didn't used to do that. Don't know why he does it now
I'm pretty sure he does that now because 1) he can't scream as well as he used to be able to, and 2) because he wants to still be able to sing for the next 5 or 10 years.
Chester's voice is one of the epicness voices I've ever heard from a singer. And his screams never getting lost over the past years. I can understand that he screaming less than in the past. Linkin Park wrote very hard songs to sing. He need his air to sing the right notes for example Shadow of the day, where he failed very often. New Divide is a song that is hard to sing, or older songs like crawling where he put much energy in the chorus, then it is hard to scream that shit with full power, but his screams are very epic after all.
He can still scream with the best of them, he just chooses not to do so more often now. Pretty much end of story.