...
(Grey: TAC reports but no BUFR, Purple: BUFR reports but no TAC, Red *: position error. Blue: both BUFR and TAC, light blue indicates fewer ascents in BUFR. Triangle - ship report, X - wind-only report.)
The plot below distinguishes native BUFR (stations reporting valid radiosonde drift positions): high/low resolution (dark/light blue, using 300 level threshold) from reformatted TEMP (orange). There are now high resolution reports from all continents.
Almost all reformatted TEMP reports are sent as separate parts (A/B/C/D), this is contrary to the BUFR coding rules (there should be a single report containing data for the whole ascent) and reformatted TEMP reports are regarded as unusable by ECMWF and most other NWP centres. BUFR reports generated directly from the radiosonde raw data are much better.