Internet usage around the world, especially in the wealthiest countries, has steadily risen over the past decade and it shows no signs of slowing. According to a report by the Internet trend investment firm Kleiner Perkins Caulfield & Byers, 245 million people in the United States were online as of 2011, and 15 million people connected for the first time that year. As Internet usage grows, online commerce grows with it. This means that more people are using the Internet with each passing year, and enough of them are spending money online to impact the economy in significant ways. (See also E-Commerce Marketing)
A backlink is a reference comparable to a citation. The quantity, quality, and relevance of backlinks for a web page are among the factors that search engines like Google evaluate in order to estimate how important the page is. PageRank calculates the score for each web page based on how all the web pages are connected among themselves, and is one of the variables that Google Search uses to determine how high a web page should go in search results. This weighting of backlinks is analogous to citation analysis of books, scholarly papers, and academic journals. A Topical PageRank has been researched and implemented as well, which gives more weight to backlinks coming from the page of a same topic as a target page.