On June 6th, on the heels of a core update, Google announced that a site diversity update was also rolling out. This update offered a unique opportunity, because site diversity is something we can directly measure. Did Google deliver on their promise, or was this announcement mostly a PR play?
There are a lot of ways to measure site diversity, and we're going to dive pretty deep into the data. If you can't wait, here's the short answer — while Google technically improved site diversity, the update was narrowly targeted and we had to dig to find evidence of improvement.
How did average diversity improve?
Using the 10,000-keyword MozCast set, we looked at the average diversity across page-one SERPs. Put simply, we measured how many unique sub-domains were represented within each results page. Since page one of Google can have less than ten organic results, this was expressed as a percentage — specifically, the ratio of unique sub-domains to total organic results on the page. Here's the 30-day graph (May 19 – June 17):
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A site diversity of 90 percent on a 10-result SERP would mean that nine out of ten sub-domains were unique, with one repeat. It's hard to see, but between June 6th and 7th, average diversity did improve marginally, from 90.23 percent to 90.72 percent (a 0.49 percent improvement). If we zoom in quite a bit (10x) on the Y-axis, we can see the trend over time:
Zooming in to just a 10 percent range (85–95 percent diversity), you can see that most of the change happened in a single day, and the improvement has remained in place for the week since the update. Even zooming in, though, the improvement hardly seems impressive.
Was the improvement more isolated?
Being as fair to Google as