Faith group memberships are always in flux and there are a lot of "free range" heathens out there, as a friend of mine puts it.

Many people choose to be independent (or part of a local kindred or Garth only) rather than affiliate with any large organizations such as Troth, AFA, or AA.
I look at it this way... one million people self-identified as "new age, Wicca, pagan, or other" in the last U.S. Census on religion. If just one percent of that figure is Asatru, that's 10,000 people... but of course that is not at all scientific and the numbers could be wildly different either way.
One thing is for sure, the numbers are constantly rising. More and more new people have joined the Northeastern community in recent years and one of the non-affiliated chat groups for the region has close to 600 members.