The first Google index in 1998 showed 26 million pages. In 2000, the one billion mark was reached. By 2008, there were one trillion unique URLs on the web at once. Google finds all of these URLs by starting with a few initial pages and following links to inner pages, then more inner pages and so on. Many webpages are exact duplicates of each other or autogenerated content, but Google rules these out of statistics. In terms of total possible pages, Google says they are "infinite" because their search engine does not track every possible link, for instance the "next day" links on calendars which may lead to more links, etc. To keep up with the high volume of data, Google now downloads the web continuously. In terms of exploration, the search engine explores every road and intersection of the cyber-world multiple times per day.