Which search engine do seniors prefer?

Is it Yahoo? Bing? Google? Is there a study? I'm doing a report for class and I need to focus on older age groups. I can't seem to find information more recent than 2005 that breaks down search engine preference by age. I am looking for some information that is at least from the past 3 years. Thank you!
Update: I'm really looking for a study about searching behavior. Similar to the graph here: http://www.shimonsandler.com/search-engine-usage-by-age-groups/ but with more recent data points (that one is for 2005).

Thank you so much for the answers so far!
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