Beginning in the 2009, Nephrology became one of the final medical subspecialities (along with Endocrinology) to join the Medical Specialties Matching Program (MSMP), a division of the National Residency Matching Program, a.k.a. "The Match." Prior to this, individual nephrology fellowship programs had their own individual application process in which the decision to offer fellowship positions to applicants was highly variable. A recent article in CJASN describes the history of the Nephrology Match and how its adoption has been received by Nephrology Fellowship Program Directors (the article says that it has been received generally favorably).
Not every Nephrology Fellowship Program participated in the Match: 14 out of 135 programs ERAS-registered, Match-eligible programs declined to participate, citing "concern over losing local applicants to other programs, concern over waiting until June to lock in applicants, and concern over the number of potential applicant interviews" according to the CJASN paper.
A few other interestings statistics: Nephrology had by far the most foreign nationals (49%) successfully matching as first-year fellows than any of the other medical specialties (33% on average). Interestingly, of the 230 applicants who did not match, only 17 were graduates of U.S. medical schools, indicating that there is a real lack of interest by U.S. internal medicine residents to go into nephrology.
One measure of success of "The Match"--especially from the fellow's perspective--is what percentage of applicants got their first choice. About 62% of applicants matched at their first choice while about 82% of applicants matched within their top three. Also indicative of success was the fact that 95% of spots offered by Nephrology programs
Nephrology ranked fifth in the total number of applications, behind (in decreasing order of popularity) Cardiology, Heme/Onc, GI, and Pulm/Critical Care.