Just dealing with numbers like this is a receipe for misleading conclusions, IMHO. Sales up could be because there was a discount offered! NC's down could be because the auditors were lazy or didn't know what they were looking at!
As an ex-third party auditor, in the 'old days' of ISO registration one question I was frequently asked was "How do we compare on the number of NC's to other companies?"

What kind of question is that?
Any statistics like these numbers are meaningless without knowing the data behind them. See also the recent thread about what gets reported at Management Review from the Internal Audits.............