A call analytics system for analyzing the effectiveness of advertising campaigns using performance data and call data. Specifically, the call analytics system evaluates the performance of different keywords in generating calls to displayed phone numbers. The call analytics system uses statistical techniques to correlate received calls to displayed phone numbers with those keyword or keywords that were associated with displayed advertisements. The system gives advertisers the ability to track and measure which keywords drive sales for mobile users that call advertisers directly from ads on their smartphones or other mobile devices. In some embodiments, the system uses the calculated effectiveness of certain keywords to recommend changes to present or future advertising campaigns of the advertiser.