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NCSA Compares Google and Yahoo Index Numbers
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. "
Honestly, when I first heard the news over the weekend I thought "rubbish, they must be ignoring requests for spiders to go no further or something." I guess NCSA can either 1) Expect no gifts from Yahoo OR 2) Report significantly different results after a sizable gift to NCSA.
75% less truth than other leading brand
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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
"Based on the data created from our sample searches, this study concludes that a user can expect, on average, to receive 166.9% more results using the Google search engine than the Yahoo! search engine. In fact, in the 10,012 test cases we ran, only in 3% of the cases (307) did Yahoo! return more results. In 96.6% of the cases (9,676) Google returned more results. In less than 1% of the cases (29) both search engines returned the same number of results. It is the opinion of this study that Yahoo!'s claim to have a web index of over twice as many documents as Googles index is suspicious. Unless a large number of the documents Yahoo! has indexed are not yet available to its search engine, we find it puzzling that Yahoo!'s search engine consistently returned less results than Google. "
but they can't sift through it nearly as well as Google, so what does it matter? Even if you have a bigger dictionnary, if you can't speak English at all it won't do you much good.
I never spellcheck and I freely admit it. Save your karma for more worthwhile "lol erorrs" replies
Sorry, but if Google consistently returns more results, it could just as easily mean that the filtering isn't as good.
I still prefer Google though.
In other words, they believe Google indexes more items based on their own tests of searching.
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They only used words from the English Ispell word list. Besides the english-language bias, this is probably limited in other ways. News websites use a limited vocabulary, but a lot of proper names -- so if one engine indexed these better, they wouldn't necessarily get a better rating. News sites are also very dynamic and have a large number of webpages, so they would be influential in the count.
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Yahoo returns a lot of dupes.
They may have more unique information simply futher down the result list, but since the search engines terminate the results at not quite 1k (1,000), the researchers have no way of testing that out.
All they can really show is that google returns more unique results per 1000 (which usually means that more items are indexed, but could be from Google's Pagerank also)...
There is always a frontier where there is an open and willing mind
TFA notes that queries with greater than 1,000 results were dropped from the survey, because Google and Yahoo both truncate their results to 1,000.
That makes sense, but it does stand to reason (or, at least, to my reason) that these queries that garner large numbers of results could have had a significant impact on the bottom line of the survey.
Those could be the larger sites, where Yahoo is perhaps digging deeper, requesting data from forms, ignoring robots.txt, etc. It could be where they're getting those big claimed numbers of indexed documents.
I don't know about the study but that is the most readable perl code I have seen in a long time.
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!
The very methodology used in this case seems rather incorrect to me.
The assumption (as stated in the paper): Since Yahoo claims to have indexed twice as much as google, searches should return twice as many entries.
That assumption is flat out incorrect. There are actually multiple problems.
First, the scope of the search (based on index terms) is really up to the search engine itself. Since each search engine does not return the entire database as search results, it is very much up to the individual search algorithm to determine the depth of entries considered to 'match' a set of terms. That's what is really being reflected in these results.. it is not the overall size of the index, but simply how aggressive the search algorithm is in matching terms to entries.
Even if the algorithms where identical (same algorithm being run across both indexes), the nature of search does not scale in that way. If Yahoo has, for instance, becomre more aggressive in indexing message board and forum content, then only searches that play to those subjects should return more results than Google. Since searches are by definition narrowing on a data set, a methodology needs to be developed that more effectively tests the BREADTH of the results more than simply testing the depth.
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The study only checked English words. Is it possible that the increase came from Yahoo expanding into more international website markets?
Just a thought
Seriously. 'We wrote a script and here are the results'? This would take an average PERL programmer what -- 30 minutes of work? Has academic research in computing really sunk to this level?
Maybe it's not even worth pointing out how badly flawed (and lazy) the underlying assumption of 'twice the results = twice the index size' probably is, as I'm sure we're going to see a few dozen posts to that effect (unless PageRank really means nothing), but at least I can complain about the slant they put on this, and how strong a conclusion they seem to derive.
The top of the page return for Yahoo is
"Failure on eBay Find failure items at low prices. "
which illustrates the most important difference between Yahoo and Google.
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Google started treating plurals as the same search about a year ago. Yahoo doesn't. So, if you google for "inkjet printers" and "inkjet printer" you will get the same result set; however, on Yahoo, you will get different results.
The net result is that for the same index size, Google will return more results. (And, IMHO, more meaningful ones.)
So in the conclusion, the author writes that since Google displayed more results, based on their random test data, it was the superior search engine? That seems so wrong somehow...
Wouldn't a better search engine return less, but more appropriate results? I mean, how many of us have found the information we were actually looking for on page ten or twelve of a search. And, isn't less more, but better? %insert Linux geek laughs here%
One would think that volume of results would not a better search engine make, although it may indicate a larger engine index size; an expicit statement to that effect seems to be missing from the NCSA report.
-Runz
Google only reports "about 4,820,000" entries for Britney Spears, while Yahoo reports "about 67,100,000" entries! This makes Yahoo more than 12 times better than google! Yeah, my methodology is completely fucked up... but then, so is the NCSA's!
I've abandoned my search for truth; now I'm just looking for some useful delusions.
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.
Of course the study also demonstrates that on the searched terms, Yahoo's estimate numbers vastly overestimated the number of available results they actually found. So if the pages from the study are even close to representative in that regard then this would make the numbers you quote utterly meaningless.
Which is the entire reason, of course, why they kept the limits under 1,000 in the first place-- that for any number over 1,000, if the search engine says, say, "I found "2.5 million results for 'Valerie Plame'", you have no way to tell whether it's telling the truth or not.
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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.