31 mostly early-stage startups have been acquired by Twitter since 2008. On average, acquired startups with funding raised just 2.4 rounds, with only six ever reaching the Series B stage.

Last week, Twitter announced via tweet that it has submitted filings to the SEC for its much-hyped initial public offering, a big milestone for the microblogging service that launched in 2006. Since its launch, the company has made M&A a key part of its growth strategy acquiring 31 startups specializing in social TV analytics to crash reporting solutions to malware scanning software.

Below is some data on these 31 acquisitions and acqui-hires including at what stage Twitter tends to acquire startups, which VCs invest in eventual Twitter acquisitions and where Twitter-acquired companies tend to be based geographically.

Of the 31 Twitter acquisitions, 18 have come since the start of 2012 highlighting the company’s accelerated pace of acquisition. In total, the startups acquired raised $73M in funding across 42 transactions prior to being acquired by Twitter. Bluefin Labs was the most well-funded of the bunch, followed by just-acquired mobile ad exchange MoPub which was backed by investors including Accel Partners and Harrison Metal.

Of the acquired startups that raised funding, only six ever reached the Series B stage. Nine startups including Ubalo and Lucky Sort were acquired by Twitter after receiving just seed or angel funding. On average, Twitter startups with funding raised 2.4 rounds prior to acquisition. And the average time between first funding and acquisition was 2.1 years.

Peeling back Twitter’s acquisitions by geography, we see that 58% of Twitter’s acquired firms were based in California. 10% of acquisitions each were for New York or Massachusetts-based companies. Twitter also completed several acquisitions for internationally-based startups including Canadian social news reader Summify and UK-based Tweetdeck.

There are several investors who have backed three startups acquired by Twitter, all of which are early-stage funds – Harrison Metal, Lowercase Capital and SV Angel. Perhaps not surprising to see Chris Sacca-run Lowercase Capital on the list as Sacca was an early investor in Twitter.

In addition, three of the acquired companies, AdGrok, BackType and Posterous, were Y-Combinator graduates. Below is a list of the investors that have backed two or more startups acquired by Twitter since 2008.

  • SV Angel
  • Lowercase Capital
  • Y Combinator
  • Harrison Metal
  • Ron Conway
  • Naval Ravikant
  • First Round Capital
  • Founder Collective
  • Redpoint Ventures
  • Accel Partners
  • Bill Lee
  • JAFCO Ventures
  • Betaworks
  • Lerer Ventures

For reference, all 31 of Twitter’s acquisitions and acqui-hires along with their date of acquisition are below.

  • MoPub (09/2013)
  • Trendrr (08/2013)
  • Marakana (08/2013)
  • Spindle Labs (06/2013)
  • Lucky Sort (05/2013)
  • Ubalo (05/2013)
  • We Are Hunted (04/2013)
  • Bluefin Labs (02/2013)
  • Crashlytics (01/2013)
  • Cabana (10/2012)
  • Vine (10/2012)
  • Clutch.io (08/2012)
  • Nclud (06/2012)
  • RestEngine (05/2012)
  • Hotspots.io (04/2012)
  • Posterous (03/2012)
  • Dasient (01/2012)
  • Summify (01/2012)
  • Whisper Systems (11/2011)
  • Julpan (09/2011)
  • Bagcheck (08/2011)
  • BackType (07/2011)
  • AdGrok (05/2011)
  • TweetDeck (05/2011)
  • Fluther.com (12/2010)
  • Dabble DB (06/2010)
  • Cloudhopping (04/2010)
  • Atebits (04/2010)
  • Mixer Labs (12/2009)
  • Values of N (11/2008)
  • Summize (07/2008)