Below is an infographic depicting the search trends for Visa, MasterCard and American Express from 2007-2011 for 33 countries. I have used Google Trends to collect the for data last 5 years. You can sort the data by Country or by Year. The key words used in the analysis are 'visa' 'mastercard' and 'amercian express' in the Financial Services Category.
According to Google - The data reflects how many searches have been done for a particular term, relative to the total number of searches done on Google over time. They don't represent absolute search volume numbers, because the data is normalized and presented on a scale from 0-100.