In the wake of yesterday’s announcement of an ad deal between Google and Yahoo, Hitwise’s Heather Hopkins examines the search audiences of the two firms, finding a greater propensity by Google users to have spent greater than $500 online.

Moreover, Yahoo Search users skew younger than Google’s, but the age gap has closed slightly since February, she finds, using parent-company Experian’s Mosaic USA segmentation.

Yahoo Search has distinct strengths among some segments, whereas Google’s strengths lie in others:

For example, “Aspiring Contemporaries” are over-indexed on Yahoo in relation to the entire online population, whereas “Affluent Suburbia” is over-indexed on Google. (The Hitwise post provides segment definitions.)

According to Nielsen figures, Google’s share of searches in April was 62%, compared with less than 18% for Yahoo: