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NCSA Compares Google and Yahoo Index Numbers

Posted by ScuttleMonkey on from the searching-for-truth dept.

chrisd (former Slashdot editor and now Google employee) writes "Recently, Yahoo claimed an increase of index size to "over 20 billion items", compared to Google's 8.16 billion pages. Now, researchers at NCSA have done their own, independent, comparison of the two engines. "

5 of 395 comments (clear)

  1. Accurate results? by bigwavejas · · Score: 5, Interesting
    Google sometimes returns some pretty interesting/ entertaining results.

    Try searching for the word, "failure" in Google and check the results.

    This brings into question *accurate* results. In this case it appears that's left to interpretation.

    --
    "Simplify, simplify, simplify!" Thoreau
  2. The results by Swamii · · Score: 4, Interesting
    For those that don't want to read the flippin' article:

    Based on this random sample, we found that on average Yahoo! only returns 37.4% of the results that Google does and, in many cases, returns significantly less.


    In other words, they believe Google indexes more items based on their own tests of searching.
    --
    Tech, life, family, faith: Give me a visit
  3. More please! by 2008 · · Score: 5, Interesting

    This is a great article! I wish there were more like it on slashdot. It's scientific instead of an opinion piece, it has references, it's repeatable. It's also short and very readable, unlike a lot of science papers.

    OK, it is yet another Google piece, but it's not "some junior analyst predicts Google will buy Apple and release OSX86box 720".

    --
    I quit!
  4. Proper name samples by jkauzlar · · Score: 5, Interesting
    Let's try a few samples of proper names:

    Search: Valerie Plame
    Google: 908,000
    Yahoo: 2,580,000

    Search: "Boulder, Colorado"
    Google: 1,600,000
    Yahoo: 5,880,000

    Search: "Linus Torvalds"
    Google: 2,560,000
    Yahoo: 5,870,000

    I assume it goes on like this. Of course these exceed the 1000 maximum hit limit given in the study.

  5. Holy lack of IR stastics understanding, Batman! by freality · · Score: 4, Interesting

    The most basic measure of performance in Information Retrieval is precision vs. recall.

    Precision is how many of the results that you return are correct. e.g. If Google returns 100 results and 10 of them are correct, then the precision on that query is 10%.

    Recall is how many of the correct results you return. e.g. If Yahoo returns 100 results out of a total 1000 correct matches, then the recall on that query is 10%.

    Information retrieval systems such as search engines balance these two metrics -- which are fundamentally at odds with each other -- to give the "best balance" in the eyes of the system's designers.

    The NCSA study basically misses the effect this decision would have on perceived size of index.

    A simple demonstration shows how it works.

    First let's say both search engines have the same index size: 10B pages. Second, let's say both search engines have exactly the same apriori capability for precision and recall, but can tune for a preferred performance. Yahoo decides it wants to favor more precise results over more results recalled, at a 2:1 relative ratio compared to Google.

    In that case, any given query will show half the hits from Yahoo as compared to Google. Concluding Yahoo's index to be half the size of Google's, given this result, would be incorrect.

    Furthermore, without knowing the precision/recall performance of either system, they can only demonstrate a lower-bound on index size, and that certainly doesn't predict average or max index size.