What does Twitter's deal to allow Google full, real-time access to its stream of tweets mean for search results? How many tweets are getting indexed? Which types of tweets are valued most by the search engine?

Stone Temple Consulting recently set out to answer those questions by examining a sample of 138,635 tweets of various type (text-only, photo, video, etc.) from a range of account types (40% people/brands with 10,000 or more followers).

The vast majority of tweets are still not making it into search results, with only 7.4% of the sample tweets getting indexed by Google, the analysis found.

However, tweets from accounts with 1M+ followers have a much higher likelihood of getting indexed, with 21% of such messages appearing in search results.

As the report notes, this doesn't necessarily mean that Google's crawlers are looking at Twitter follower count specifically, since other signals could be coming into play. It does at least indicate that the search engine is valuing tweets more from authoritative profiles.

As for tweet type, tweets with images are the most likely to be indexed (12% of the sample appeared in search results). Tweets that include hashtags are also more likely to be indexed.

Inbound links from third-party sites have the biggest impact on influencing whether a tweet gets indexed, the analysis found.

Some 26% of the sample tweets with at least one inbound link from a site other than Twitter got indexed by Google. Moreover, the tweets with the most inbound links (100+) had the highest likelihood of appearing in search results (46%).

The researchers did not measure the nature of these inbound links, but it's likely that quality has an impact, as is the case with Web pages.

About the research: The report was based on data from a sample of 138,635 tweets of various type (text-only, photo, video, etc.) from a range of account types (40% people/brands with 10,000 or more followers).