The Mass Effect Wiki says that krogan females can produce up to 1,000 fertilized eggs in a year. However, we also know that Tuchanka is an insanely dangerous place to live: between the thresher maws and the nuclear devastation and the other krogan that will no doubt be trying to kill you from the moment you're born, I think it's safe to say that not all 1,000 of those eggs will reach adulthood. In fact, the krogan birthrate is probably an adaptation to compensate for that exact problem.
Then, obviously, the Genophage dropped that number even further. However, there seems to be some confusion about how much: Wrex and the krogan keep insisting that their race is going extinct, but Mordin and the salarians are steadfast in their belief that they merely "stabilized" the krogan birthrate. I always understood that it was the krogan's warlike nature that pushed them from "stable" to "declining," but the females' inability to have even one child does seem excessive.
Do we ever get a good idea of how fast the krogan population actually grows, once you factor in all those variables? Are there any comments in the games or the books or the comics along the lines of "they could fill a whole world to capacity in ten years" or "the Patriarch has six thousand children"? And then once the Genophage started, do we ever get an effectiveness rate (like "prevented 96% of all births" or "dropped female fertility to one viable birth every four years")?