For the California region (state of California plus the California Floristic Province sections of Oregon, Baja California and the Sierra Nevada portion of Nevada), there are 4064 endemic vascular plants by my estimation. I have counted them from Munz & Keck 1959, Munz 1969, Hickman 1993 and other regional floras.
Raven & Axelrod (1977) tallied 2125 endemics – 47.7% of the total flora
Baldwin et al. (2012) tally 4976 native species and 1315 endemic full species – 26.6% of the total flora endemic. Their estimate is off the mark because endemic infrataxa are omitted.
Adding the 912 treated endemic infrataxa to their 1315, with 6502 native taxa, results in 34.2% endemic
My count includes 147 endemics confined to Baja California, 34 confined to southwest Oregon, and two in the Sierra Nevada portion of Nevada – 183 taxa.
My tally includes 501 taxa not treated in Baldwin et al. (2012) but which were treated in a previous state flora.
My tally includes 2414 endemic taxa treated as full species in Baldwin et al. (2012) - much higher than reported in their Appendix (page 1520-1521)
If we take the Baldwin et al. (2012) tally of 6502 and my estimate of 4064 endemics – the rate is 67% - the highest rate yet reported.