attach a percentile figure to reviews.

Grade inflation cannot be fixed, and maybe shouldn't be.  

What can be, and should be done, is to point out where a given number stands.

I'll bet that a 7 is 50th percentile.

It should be weighted according to the individual reviewers who have provided that particular providers reviews.

For example, let's say that the average performance score given by these reviewers for all the providers that they have seen is a six.  In that case, if this particular provider gets a seven, that's pretty good.

On the other hand, If these reviewers' average score is an eight, then a seven is sub par, so to speak.

It would take quite a bit of number crunching or a really elaborate program to manage this, but it's probably doable and not a bad idea, really.

it's just a matter of letting people know where the markers really are