Comparing Google Trends for Websites and Google Analytics data. 2011 Edition

In June 2009 I wrote an article comparing charts and data provided by Google Trends for Websites and the one coming from Google Analytics, for the same site of course.

This is 2011 edition and these are the details:

  • Period of study goes from November 2010 to November 2011, 12 months
  • Charts from Analytics show data by weeks to shape trend lines as close as possible to Google Trends for Websites ones
  • All charts show unique visitors

Without further ado let's face data side by side from 9 different sites to see how well or bad they match.

Compare Google Trends for Websites and Google Analytics data

Google Trends versus Analytics

How Google gathers data for Trends is described in this page, something you can guess yourself with a bit of imagination and taking into account how they are cannibalizing everything in the internet. Google Analytics is mentioned as one of the sources not surprisingly.

What we can infer from this comparison?

  • Most of the trend lines at GTS (Google Trends for Websites) charts achieve a decent grade of similarity with GA ones
  • Ups and downs are slightly more exaggerated at GTS charts
  • Even when we know they have Google Analytics accurate data they never match exactly. Is done in purpose? If I were Google I would do it

What about the numbers, do they match too?

The numbers below are very rounded because of the little information we have from GTS charts, just numbers in the vertical axis that makes them a rough approximation. In any case what it relevant here is the deviation.

  • GA shows 1,143K unique visitors a week, this means
    ~163K a day - GTS ~142K a day. Deviation -13%
  • GA ~171K - GTS ~120K. Dev. -30%
  • GA ~53K - GTS ~23K. Dev. -57%
  • GA ~100K - GTS ~60K. Dev. -40%
  • GA ~114K - GTS ~70K. Dev. -39%
  • GA ~36K - GTS ~30K. Dev. -17%
  • GA ~16K - GTS ~16K. Dev. 0%
  • GA ~6.5K - GTS ~5.8K. Dev. -11%
  • GA ~64K - GTS ~50K. Dev. -22%

In average Google Analytics numbers are 25% higher than the ones shown in Google Trends for Websites but, a big blinking 'but' here, there are cases where GA shows double than GTS while some other numbers match so you are never going to know how far from reality numbers from GTS are if you are checking competitors traffic for example.

Differences with the comparison made in 2009

A couple of them:

  • In 2009 last quarter of Trends tended to be less accurate compared to Analytics. This issue seems to be solved now
  • Actual trends lines in GTS charts seem a bit more faithful to the ones pulled from Analytics data

In general terms Google seems to be doing a better job on accuracy with the charts available at GTS lately.

Next time you show one of those Google Trends charts to somebody and he / she despises them saying they are unreliable show also to this person how good they mimic real data.

Jan 09, 2012
Written by:
Filed under: Analytics
3 comments







3 comments
Jan 09, 2012
Posted by:
Nico Lawsons #1

Nice blog post, didn't know these graphs were so alike. Time for some extra research!

Good work :)

Jan 09, 2012
Posted by:
Michael Notté #2

Interesting post. I did a similar exercise back in 2009 but comparing GTS data with WebTrends data (i.e. not GA). It was "amazing" to see that in spite it was not using GA data - the global trend line were quite similar (check here http://www.kaizen-analytics.com/2009/10/google-trends-for-websites-do-you-trust.html)

Of course total number were quite different but I have always used GTS for global trends and relative comparison (vs. competitors) - not for comparing actual volume.

Thanks for sharing this.

Michael

Jan 09, 2012
Posted by:
Ani Lopez #3

Thanks Nico and Michael for your comments.

Michael, you were not lucky with the 2 examples mentioned in your article, Google Trends works quite well. Thanks for sharing it

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