Every step every applicant makes can be tracked from MCAT attempts and application starts through submission, interviews, matriculation, step exams, into residency and beyond. AAMC/AMCAS, AACOM/AACOMAS, ACGME, and all the other organizations make this most of data publicly available of at least estimable from sources
https://www.aamc.org/media/5976/download shows 990,790 applications submitted with 22,712 matriculants enrolled for 2022-2023 matriculation year. Other AAMC FACTS tables report 55,188 applicants
https://www.aamc.org/media/50081/download Question #15 shows about 52% matriculants had more than one acceptance of 47% how to single acceptance.
The aggregate number of interviews is an estimate from the applications received and interviews offered as reported on each school in the MSAR.
The number of acceptances is from end-of-the-year report, compiled by AAMC That isn’t publicly available. The number of alternates is purely an estimate on my experience.