Among the Android tablet makers, Samsung lead the pack with an estimated 37 million tablets sold or about 19% of the market, taking the number 2 spot in the global tablet market (after Apple). Asus came in second with 11 million, while Amazon and Lenovo filled out the top 5 tablet makers with 9.4 million and 6.5 million tablets, respectively.
Gartner believes that Amazon only showed modest growth, increasing their sales by less than a couple million, while Samsung and Lenovo both showed explosive growth. Lenovo more than tripled their 2012 sales, while Samsung quadrupled theirs. According to Gartner, both are benefiting from their decision to target the lower end of the market; much of last year's growth is attributed to low-end, smaller screen tablets as well as first-time tablet buyers.
"In 2013, tablets became a mainstream phenomenon, with a vast choice of Android-based tablets being within the budget of mainstream consumers while still offering adequate specifications," writes research director Roberta Cozza. "As the Android tablet market becomes highly commoditised, in 2014, it will be critical for vendors to focus on device experience and meaningful technology and ecosystem value — beyond just hardware and cost — to ensure brand loyalty and improved margins."
These figures more or less agree with the estimates released by IDC in late January, though there is a discrepancy of around 22 million tablets sold. IDC also reported that Apple dominated the tablet market, though I'm not sure how either firm can now that for sure. The only solid data on the global tablet market is what Apple releases every quarter; the rest is a WAG.