I noticed that the most recent subject test is 2007, and they seem to indicate that the max score was 890 then. The 50%ile mark raw score in 2007 as indicated by the most recent available practice test was 33. The current 50%ile scaled score (here, page 22) is 640 out of what looks like a possible 920, though I've seen the occasional person claim a score higher than that so I'm not certain as to whether the scaled scores for the mathematics subject test now go up to 990, and if so, is there any way to obtain information from the ETS about raw to scaled score conversion, given that it seems to be quite different from how their most recent practice booklet indicates?
How much has the scaled score range changed over the past several years? Is it a set figure or does it vary from year to year?
Would interpolating the newer raw scores based on the old chart from the practice booklet, and the new scaled scores, be a reasonable approach to determining the present score conversion? If not, is there any alternative way to determine the current conversion?
I think just sorting out the first question (where is the current score range) would be sufficient to allow me to interpolate the given data so I can at least get an estimate.