The human process behind Google's algorithm

MOUNTAIN VIEW, Calif.--Google is famous for evangelizing the power of the algorithm. It spends less time talking about the several hundred human beings who influence its algorithm.

To work at Google is to believe in the power of automation. "We've found the best approach to search is algorithmic, it's the only thing that works at scale," said Matt Cutts, a principal engineer at Google responsible for keeping spam out of search results. "We want to use computers all the time."

The obvious reality that never seems to come up quite as often is that even algorithmic Internet search is very much driven by humans. Computers and algorithms may be what handle incoming queries and generate search results hundreds of times a second, but just as Porsche engineers design their engines with slightly different requirements than Ford engineers, Google engineers are constantly tinkering with the recipe for search results that can make or break Web businesses.

Earlier this year, Cutts said that Google "tends to make a change to our core search algorithms at least once a day." In a recent interview with CNET, he reiterated that that pace continues: just last week Google search engineers met to consider 27 separate changes to the more than 200 factors that Google uses to rank search results.

In many ways, this is a natural evolution of Google's quest to organize information. The Web changes quickly and dramatically, and a Google search recipe left unaltered would quickly grow stale and choked with spam. Yet the constant tweaks show that the internal debates conducted by a relatively small number of people can have a significant impact on the way the Internet is presented to millions.

Cutts and Google representatives wouldn't disclose exactly how many people work on search quality at Google, but he did say there are "hundreds" involved in the process at a company that employs more than 20,000 people. They are entrusted with making sure Google keeps its place atop the search world, which affords the company a steady supply of cash allowing it to pursue a seemingly limitless number of other interests.

They range from someone like John Mueller, a Webmaster trends analyst who patiently answers questions from confused site owners in Google's Webmaster Central forums, to Udi Manber, a legendary engineer listed next to Google executives such as co-founders Larry Page and Sergey Brin as the person "responsible for core search." They must balance the desire to provide the most accurate results with the griping of Webmasters knocked down a peg by algorithm changes: not to mention the constant battle by spammers to infiltrate search results.

The Webmaster forums are the first level of Google search where human representatives of the company make their presence felt. A lot of the content in the forums involves tips provided by volunteers for getting your site to rank within Google's search index, Google's trademark approach to customer service. However, representatives like Mueller wade into the discussion threads to provide a more official answer to questions about site tags or inbound links.

Mueller and his counterparts (Google is trying to keep the forums staffed around the clock) also serve as an early-warning sign for engineers higher up the food chain when considering what changes might need to be made to the way Google ranks sites. Cutts considers this a competitive advantage for Google, in that it has a constant human "debugging" system generated by the number of people who care passionately about where they rank on Google as well as engineers who closely monitor feedback in the press, social networks, and Google's forums.

Most of the time the feedback comes from those who could use a basic lesson or two in site design, ordinary small business owners who may know their business cold, but are out of their depth when it comes to search-engine optimization except that they know it's important to rank high in Google results. But on a fairly regular basis, issues generated by complaints from the outside world work their way up to Google's weekly search quality meetings. (Wired ran a good article on the behind-the-scenes process earlier this year.)

Before any such changes are formally proposed, they are tested among small groups of searchers to gather data on the impact, an essential part of the decision making process. A committee then discusses the impact of those changes: at the last meeting, 16 proposed changes required formal discussion while an additional 11 were considered uncontroversial enough to hash out over e-mail.

Each of those changes has the potential to affect search results in a big way. Take for example a recent change to present more results from a single domain when processing a search query like "apple iPhone." Google now presents results from Apple.com sites as six of the crucial top 10 results, believing someone searching that query demonstrated intent to find Apple-affiliated sites, whereas before it wanted to encourage "diversity" within that first page of results. Reviewers, retailers, and others with relevant content related to Apple's prize product suffer the consequences of being pushed farther down the page, or onto the second page.

Those affected by changes to Google's algorithms can file a "reconsideration request" if they believe they've done nothing wrong in seeing their rankings plummet, or if they've made changes to bring their sites back into compliance with Google's antispam rules. That, of course, requires a human to review the site in question and make a determination about the viability of the site.

So behind every algorithm, and therefore behind every search result, is a team of people responsible for making sure Google search makes the right decisions when responding to your query. Obviously, there's no other way it could have happened: Google is a living example of what's possible when brilliant people devise a smart algorithm and marry it to limitless computing resources.

But it also means that search results are dictated by far more than unemotional machines. No Googler sits there and responds to individual requests for "wedding venues in Lake Tahoe." They do decide, however, how Google's algorithms consider content to be relevant to such a query, and which sites are eligible to be presented in those results.