These are my notes from the talk Scaling Google for Every User by Marissa Mayer.

Google search has lots of different users who vary in age, sex, location, education, expertise and a lot of other factors. After lots of research, it seems the only factor that really influences how different users view search relevance is their location.

One thing that does distinguish users is the difference between a novice search user and an expert user of search. Novice users typically type queries in natural language while expert users use keyword searches.

Example Novice and Expert Search User Queries

NOVICE QUERY: Why doesn't anyone carry an umbrella in Seattle?
EXPERT QUERY: weather seattle washington

NOVICE QUERY: can I hike in the seattle area?
EXPERT QUERY: hike seattle area

On average, it takes a new Google user 1 month to go from typing novice queries to being a search expert. This means that there is little payoff in optimizing the site to help novices since they become search experts in such a short time frame.

Design Philosophy

In general, when it comes to the PC user experience, the more features available the better the user experience. However when it comes to handheld devices the graph is a bell curve and there reaches a point where adding extra features makes the user experience worse. At Google, they believe their experience is more like the latter and tend to hide features on the main page and only show them when necessary (e.g. after the user has performed a search). This is in contrast to the portal strategy from the 1990s when sites would list their entire product line on the front page.

When tasked with taking over the user interface for Google search, Marissa Mayer fell back on her AI background and focused on applying mathematical reasoning to the problem. Like Amazon, they decided to use split A/B testing to test different changes they planned to make to the user interface to see which got the best reaction from their users. One example of the kind of experiments they've run is when the founders asked whether they should switch from displaying 10 search results by default because Yahoo! was displaying 20 results. They'd only picked 10 results arbitrarily because that's what Alta Vista did. They had some focus groups and the majority of users said they'd like to see more than 10 results per page. So they ran an experiment with 20, 25 and 30 results and were surprised at the outcome. After 6 weeks, 25% of the people who were getting 30 results used Google search less while 20% of the people getting 20 results used the site less. The initial suspicion was that people weren't having to click the "next" button as much because they were getting more results but further investigation showed that people rarely click that link anyway. Then the Google researchers realized that while it took 0.4 seconds on average to render 10 results it took 0.9 seconds on average to render 25 results. This seemingly imperciptible lag was still enough to sour the experience of users enough that they'd reduce their usage of the service.

Improving Google Search

There are a number of factors that determine whether a user will find a set of search results to be relevant which include the query, the actual user's individual tastes, the task at hand and the user's locale. Locale is especially important because a query such as "GM" is likely be a search for General Motors but a query such as "GM foods" is most likely seeking information about genetically modified foods. Given a large enough corpus of data, statistical inference can seem almost like artificial intelligence. Another example is that a search like b&b ab looks for bed and breakfasts in Alberta while ramstein ab locates the Ramstein Airforce Base. This is because in general b&b typically means bed and breakfast so a search like "b&b ab" it is assumed that the term after "b&b" is a place name based on statistical inference over millions of such queries.

At Google they want to get even better at knowing what you mean instead of just looking at what you say. Here are some examples of user queries which Google will transform to other queries based on statistical inference [in future versions of the search engine]

User Query Google Will Also Try This Query
unchanged lyrics van halenlyrics to unchained by van halen
how much does it cost for an exhaust systemcost exhaust system
overhead view of bellagio poolbellagio pool pictures
distance from zurich switzerland to lake como italytrain milan italy zurich switzerland

Performing query inference in this manner is a very large scale, ill-defined problem. Other efforts Google is pursuing is cross language information retrieval. Specifically, if I perform a query in one language it will be translated to a foreign language and the results would then be translated to my language. This may not be particularly interesting for English speakers since most of the Web is in English but it will be valuable for other languages (e.g. an Arabic speaker interested in restaurant reviews from New York City restaurants).

Google Universal Search was a revamp of the core engine to show results other than text-based URLs and website summaries in the search results (e.g. search for nosferatu). There were a number of challenges in building this functionality such as

  • Google's search verticals such as books, blog, news, video, and image search got a lot less traffic than the main search engine and originally couldn't handle receiving the same level of traffic as the main page.
  • How do you rank results across different media to figure out the most relevant? How do you decide a video result is more relevant than an image or a webpage? This problem was tackled by Udi Manber's team.
  • How do you integrate results from other media into the existing search result page? Should results be segregated by type or should it be a list ordered by relevance independent of media type? The current design was finally decided upon by Marissa Mayer's team but they will continue to incrementally improve it and measure the user reactions.

At Google, the belief is that the next big revolution is a search engine that understands what you want because it knows you. This means personalization is the next big frontier. A couple of years ago, the tech media was full of reports that a bunch of Stanford students had figured out how to make Google five times faster. This was actually incorrect. The students had figured out how to make PageRank calculations faster which doesn't really affect the speed of obtaining search results since PageRank is calculated offline. However this was still interesting to Google and the students' company was purchased. It turns out that making PageRank faster means that they can now calculate multiple PageRanks in the time it used to take to calculate a single PageRank (e.g. country specific PageRank, personal PageRank for a given user, etc). The aforementioned Stanford students now work on Google's personalized search efforts.

Speaking of personalization, iGoogle has become their fastest growing product of all time. Allowing users create a personalized page then opening up the platform to developers such Caleb to build gadgets lets them learn more about their users. Caleb's collection of gadgets garner about 30 million daily page views on various personalized homepage.


Q: Does the focus on expert searchers mean that they de-emphasis natural language processing?
A: Yes, in the main search engine. However they do focus on it for their voice search product and they do believe that it is unfortunate that users have to adapt to Google's keyword based search style.

Q: How do the observations that are data mined about users search habits get back into the core engine?
A: Most of it happens offline not automatically. Personalized search is an exception and this data is uploaded periodically into the main engine to improve the results specific to that user.

Q: How well is the new Universal Search interface doing?
A: As well as Google Search is since it is now the Google search interface.

Q: What is the primary metric they look at during A/B testing?
A: It depends on what aspect of the service is being tested.

Q: Has there been user resistance to new features?
A: Not really. Google employees are actually more resistant to changes in the search interface than their average user.

Q: Why did they switch to showing Google Finance before Yahoo! Finance when showing search results for a stock ticker?
A: Links used to be ordered by ComScore metrics but ince Google Finance shipped they decided to show their service first. This is now a standard policy for Google search results that contain links to other services.

Q: How do they tell if they have bad results?
A: They have a bunch of watchdog services that track uptime for various servers to make sure a bad one isn't causing problems. In addition, they have 10,000 human evaluators who are always manually checking teh relevance of various results.

Q: How do they deal with spam?
A: Lots of definitions for spam; bad queries, bad results and email spam. For keeping out bad results they do automated link analysis (e.g. examine excessive number of links to a URL from a single domain or set of domains) and they use multiple user agents to detect cloaking.

Q: What percent of the Web is crawled?
A: They try to crawl most of it except that which is behind signins and product databases. And for product databases they now have Google Base and encourage people to upload their data there so it is accessible to Google.

Q: When will I be able to search using input other than search (e.g. find this tune or find the face in this photograph)?
A: We are still a long way from this. In academia, we now have experiments that show 50%-60% accuracy but that's a far cry from being a viable end user product. Customers don't want a search engine that gives relevant results half the time.