The research also finds that top brand websites appear to have a natural advantage for ranking highly in searches. Searchmetrics analyzed search results from Google for 10,000 popular keywords and 300,000 websites in order to pick out the issues that correlate with a high Google ranking. The correlations were calculated using Spearman's rank correlation coefficient, in which a correlation of +1 indicated a perfect positive correlation and -1 indicated a perfect negative correlation.
The five key findings of the study are highlighted below:
Social media's effect on search
Social signals from Facebook and Twitter now correlate very strongly with good rankings in Google's index. The number of Facebook Shares that a Web page has received appears to have the strongest association (a correlation of 0.37). Twitter is far behind Facebook but is still the sixth strongest factor on Searchmetrics' list of Google ranking factors with a correlation of 0.25.
Top brands have a ranking advantage
Despite the perception of search as a level playing field, the study found that top brand websites enjoy a ranking advantage. Some of the main factors that are commonly believed to help Web pages rank well, such as the quantity of text on a Web page and having keywords in headlines and titles, have no effect in the case of large, well-known brands.
"Surprisingly, the data show a negative correlation between these factors and rankings - contradicting traditional SEO theory," explains Marcus Tober, Searchmetrics' CTO. "So, not having keywords in headlines or having less text on a page seems to be associated with sites that rank higher.
"When we looked deeper at the top 30 results we found that this pattern really starts to emerge with highly ranked pages. And when we looked at sites that are in the top position on page one of Google - the natural position occupied by brands - this is where the negative correlation is strongest. This indicates that strong brands rank highly even without perfectly conforming to common SEO practice."
Too much advertising hurts rankings
Too many and/or excessively clumsy advertisements were presumed to be a factor in the Google Panda Update and its successors which have tried to lower the search visibility of poor quality results. The data in this study supports this assumption as all the analyzed advertisement factors returned a negative correlation (-0.04).
A deeper analysis revealed that this pattern was strongest when there was a high percentage of Google AdSense ads; rankings for pages with more AdSense ad blocks seem to drop sharply. This supports Google's statements early in 2012, in which the company said that particularly prominent, distracting or above-the-fold ads could lead to ranking problems.
Quality of links is vital
The number of backlinks is still one of the most powerful factors in predicting Google rankings (with a correlation of +0.36). To get the most benefit, however, it appears a site needs to have a spread of links that looks natural - not like it was artificially created by SEO experts.
This means that a site should not simply have a large number of perfectly optimized links that include all the keywords it wants to be ranked for in the anchor text. It needs to have a proportion of 'no follow' links and links that contain 'stopwords' (such as 'here', 'go', 'this').
Keyword domains still attract top results
Contrary to reports, websites with keywords in the domain name such as cheapflights.com still often top the rankings (correlation of +0.11). Although Google has repeatedly said that keyword domain sites will slowly weaken in power in searches, this does not yet seem to be the case.
"We collated the data for our research in February and March 2012, meaning that it takes into account the impact of Google's various Panda algorithm updates that have greatly changed the look of search results since early 2011," explains Tober. "We conducted similar studies in the UK, Germany, France, Spain and Italy and found very similar results across the board, which seem to show that these findings apply internationally."
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