So now that we have the full data from both XM and Sirius for 4Q06, let's look at my favorite metric: gross subscribers. Again, the reason why I like looking at gross subs is because it shows an untainted view of market penetration. 

And what a difference a year makes.

Looking at 2005, it's clear that XM held the dominating position in gross subscriber additions. Even in the fourth-quarter of 2005, XM still held out past Sirius even despite "the Stern Effect" (now being referred to as "the Stern Bubble" by Sirius management). When 2006 rolled around, XM still continued to hold its own, but by Q4 Sirius made a massive jump.

For the first time in satellite radio history, Sirius outpaced XM in gross subscribers for the quarter. This is significant.

Sirius now is at nearly the same number of subscribers as XM was a year ago. In 2006, the reasoning behind XM's poor net subscriber additions was that churn restricted net growth. I'd be interested to see if Sirius follows this trend, or whether they will be able to learn from XM and keep churn in check.

Either way, it's clear that for the moment, the tide has turned.