The test, available to verified Google Plus accounts, adds a social element to search results.
Dell.com and OfficeMax.com had the top consistency ratings among large retailers last month.
Dell.com had the best Internet Explorer consistency score among large retailers tested in April, says Compuware Gomez. Last month, Dell.com had the most consistent site loading time with a variation of 0.49 seconds. Williams-Sonoma.com (0.67 seconds), placed second in Internet Explorer tests and was followed by LLBean.com (0.74), Newegg.com (0.77) and OfficeMax.com (0.80 seconds).
OfficeMax.com had the best Firefox consistency score in April, Compuware Gomez reports, with an average variation of 0.41 seconds. OfficeDepot.com (0.68 seconds), QVC.com (0.70), Williams-Sonoma.com (0.71) and Dell.com (0.82) rounded out the top five in Firefox testing.
The average Internet Explorer consistency score among the 18 retailers measured last month was 1.38 seconds. The same group of retailers produced an average Firefox score of 1.90 seconds.
The consistency ratings take into account differences in the speed of web page delivery across multiple visits.