Google began letting users set locations so the search engine could factor proximity into results when appropriate.
Proposed changes to Google's formula are first tested on a separate set of computers that imitate real-world search.
Those deemed worthy are next sent to evaluators around the world who act as online searchers and rate the relevance of results in various languages and regions.
Google then does live testing, with promising algorithm enhancements carefully blended into results served up by the main search engine.
"At any given time, some percentage of our users is actually seeing experiments," Huffman said.
"It is interesting because users don't know what is happening," he continued. "Of course, we don't put things out there that are terrible; we have filters to know when something is bad."
Plenty of improvements are ahead, particularly regarding the ability to understand and derive inferences from the world's many languages, according to Huffman.
He bristles at any suggestion by Google critics that results are tampered with to favour advertisers or achieve other business ends.
"If you think of the scale of what we are talking about, it is almost absurd to say we could rig results," Huffman said, noting that Google handles more than a billion searches daily.
For five and a half years he has run weekly meetings at which changes to Google's search algorithm are decided. Revenue implications of changes have never been brought up at those meetings, according to Huffman.
"Not only do we not make decisions that way, we don't even look at those numbers," Huffman said.
Google believes that delivering the most relevant search results to people as fast as possible is best for the California company's bottom line and, by extension, steers away from useless "spam" websites and "content farms".
"If we care about our users - don't care about money -- everything else just falls in line," Singhal said. "A healthy web and happy users are key to our future."
Singhal pictured a day when search engines understand users so well that they predict what people wanted to know and cue them with messages on smartphones.
"That is the ultimate dream," Singhal said. "We are nowhere close to that yet."
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