I'm not sure but I know I reached more than Gold (68 nights) but less than Platinum (75 nights) , was feeling blue that I would lose my Elite benefits when lo and behold a package arrived with a Platinum Elite card. The letter acknowledged that I didn't have enough nights but that I had been renewed anyway. My hunch is that because I tend to stay at very high revenue properties and also frequently book multiple rooms ( for myself and my biz colleagues ) and that someone had the smarts to realize that it all that added up to a good investment. Given that I was considering moving to Starwood since I didn't have the Platinum bennies I feel this was a win win and am happy to stay w/ Marriott. Cheers!