Keyword Quality Score in Adwords is very important in determining the CPC. Unfortunately, it was not possible to see the quality score in the past.
If you wanted to investigate a keyword and set the time in AdWords a year ago, you still saw the current Quality Score. You could not see if your quality score was improved.
Recently, we announced that AdWords was making the historic quality score visible. Now, the historical quality score is really available in accounts.
In a campaign, click on the “keywords” tab, then click “columns” on “QualityScore” and then add the “Qual.Score (hist.)” Column.”