The false conviction rate is estimated to be >4%.

http://phenomena.nationalgeographic.com/2014/04/28/how-many-...

That's 4% for people who are sentenced to death.

The rate for those sentenced for lesser crimes is likely much higher, due to plea bargaining ("plead guilty to petty theft or we'll charge you with grand theft").

That's not really what we're talking about here, though. We're talking about the rate of conviction of those who are proven conclusively to have lied resulting in someone else being convicted of a crime.

Generally such people receive no consequences at all.

For instance, as far as I know the woman in this case:

https://en.wikipedia.org/wiki/A_Rape_on_Campus

has not been charged with anything, despite falsely accusing an entire fraternity house of rape.