According to a report at Excite Money & Investing (based on a study by WebSideStory) a conversion to a sale is more likely when the user comes to a site from a search. It seems that the study differentiates between searches (including targeted PPC), banner ads, shopping search sites and direct navigation/type-in.
Search Sites Better At Getting Shoppers To Buy: Study

• Direct Navigation/Bookmarks 4.23%
• Search Engines (incl. PPC) 2.30%
• Banner Ads/Content related ads (Other) 0.96%

The study, by researchers at WebSideStory Inc. (WSSI), found that search sites produce more than twice the conversion rate of many other Internet marketing efforts. The study defines conversion rate as the percentage of visitors to a site who view an ad or clicking on a search result and purchase a product or service. [...]

According to the research, search sites had a conversion rate of 2.3%, meaning that for every 100 consumers clicking on a search result or advertisement, 2.3 people made a purchase. Online banner ads, shopping search sites and other online marketing efforts had a conversion rate of 0.96%, the study found. [...]

Consumers who went directly to a company’ site without using a search engine – perhaps because they set a bookmark – had a much higher conversion rate of 4.23% .

I’d love to see a more detailed breakdown showing the difference in the conversion ration between “search” by direct navigation and search engine. I am quite surprised that shopping/price search engines (is this the same?) are not doing that well. It also looks like they placed banner ads and content related ads in one category. It is not surprising that direct navigation ranks the highest in the conversion charts – after all the user most likely wanted to visit this merchant’s site for a reason.

[Thanks Wayne]