Nitpick: The vast majority of dating done today is what Dalrymple calls "age-diagnostic" dating, which means all methods that have powerful error detaction and/or correction mechanisms built in. Isochron dating is one of a few such methods. Some numbers at http://
EvC Forum: Radioisotope dating links and information -->
EvC Forum: Radioisotope dating links and information
The plurality of dating done today is with the U-Th-Pb system, and most of that is concordia-discordia dating (which is not an isochron method but is age-diagnostic).
I really wish there was a good introduction ot concordia-discordia dating on the Web. Maybe someday I'll try to write one.