Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Sirius XM Radio (Nasdaq: SIRI) are jamming out today, up by as much as 11% after the company announced full year 2011 subscriber data last night.

So what: Sirius XM shares have reclaimed the $2 threshold for the first time since August, as the company announced it ended 2011 with almost 21.9 million subscribers. Sirius XM added 1.7 million net new subscribers during the year, with 540,000 of them in the fourth quarter alone.

Now what: The subscriber gains bested the company's own subscriber guidance for the year, although the figures are preliminary. Subscriber growth accelerated in 2011 as net additions jumped roughly 20% to deliver the best year of net additions since the two companies merged. For even more color on the announcement, don't miss fellow Fool Rick Munarriz's take by clicking here.

Interested in more info on Sirius XM Radio? Add it to your watchlist by clicking here.

Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.