Traffic to e-commerce sites in the US is increasingly coming from search engines, with Google sending the lion’s share, according to new stats from Hitwise.

Websites in the Shopping & Classifieds category received 24.95% of their upstream visits from search engines last month, an increase of 0.7% over May 2006.

The proportion of those visits that were sent by Google almost doubled year on year, from 8.7% in May 2006 to 15.55% last month.

This indicates the commanding lead that Google has taken in the US search market, and the search engine enjoys similar dominance in the UK.

In the UK, Google enjoyed a massive 78% UK market share last week, even though, of all the rival search engines, Yahoo has made the biggest gains, with its share rising by 13%, though it still commands just 8.6% of the UK search market.

The figures suggest that Yahoo’s growth has occurred at the expense of smaller rivals like Ask and MSN, rather than eating into Google’s market share.

One interesting statistic from Hitwise US’s LeaAnn Prescott is that MySpace has emerged as a significant source of traffic for shopping sites. Traffic from MySpace to e-commerce sites have risen by 86.1% year on year, and the shopping and classifieds category received 3.1% of visits from the site.

MySpace’s visits increased by 67.1% in the same period, which may account for the growth. Also, retailers may have increased the amount of advertising on the social network site, or this could be the results of MySpace’s Adwords deal with Google.