I have read certain firms claim to have a 98% success rate when it comes to appeals. Then there are some that claim to have a very low rate. It all depends on the case IMO. I have written a couple briefs and won at the appeal level. If you have good medical and legal evidence you usually win. The ALJ has to have made errors that were factually detrimental to your case. You just have to find an attorney who has actually wrote a briefs to the appeals council.