Something around 500,000 for the hobby overall (U.S. participation) is probably a fairly good guess. But any number would be strictly guesswork since, to the best of my knowledge, there has been no real data gathered for a good many years. In part that's because we have a hobby made up of various subsets (scales/gauges) and it would take quite a bit of research to develop anything near an accurate figure.
Suffice it to say that we represent, despite our obvious enthusiasm, a very small portion of the overall population. And the total number is likely to continue on a downward trend over the next decade or two.
