Quick answer - you probably already found the data just didn't recognise it. PE hires from Associate 2 level upwards - usually they will hire from top performers at the Assoc grade in IBD (unlikely hire from VP+) so joining salaries are commensurate.
The actual salary in PE isn't exceptionally better than IBD - the total remuneration is about the same unless you are a principal, the main attraction is much better work/life balance, closer to clients, more involvement in the transaction process etc.
Expect salaries (excluding variables) to be in the AD/D range of IBD. Carry wont pay out for usually 7 years so may as well discount that.
