My impression when I was at MS was that they hire you at a competitive market salary, and their HR claims to do surveys and keep your yearly increases in line with market rates, however it seemed pretty easy for increases to not keep pace with market rate increases, in part because the market rate has increased pretty steadily lately.

I don't think they're the only ones with this issue. Job hoppers can get bigger raises than people staying and climbing the ladder "the old fashioned way".