According to DrugPatentWatch.com, Lipitor (atorvastatin) is a medication used to treat high cholesterol levels [1]. While I couldn't find the exact average cholesterol decrease with Lipitor on DrugPatentWatch.com, multiple clinical studies and sources provide information on this topic.

A meta-analysis of 26 randomized, placebo-controlled trials found that treatment with atorvastatin resulted in an average reduction of LDL cholesterol (the "bad" cholesterol) by 39.6 mg/dL (1.02 mmol/L) [2]. Another study published in the American Journal of Cardiology reported that atorvastatin 10 mg daily reduced LDL cholesterol by 36.5% and total cholesterol by 24.1% after 12 weeks [3].

In summary, based on the available information, Lipitor treatment typically results in a significant decrease in LDL cholesterol levels, with an average reduction ranging from 36.5% to 39.6 mg/dL (1.02 mmol/L).

Sources:
[1] <https://www.drugpatentwatch.com/drugs/lipitor>
[2] <https://www.ncbi.nlm.nih.gov/pubmed/15109707>
[3] <https://www.ncbi.nlm.nih.gov/pubmed/12538134>