According to CollegeNavigator/IPEDS, the CDS, and other federal reporting sources. The number of applicants to Stanford was as follows. There was indeed a significant increase between 2016 and 2018, but no where near 36k to 47k. Stanford will continue reporting to federal sources like this, regardless of what information they publish on their website.
2016 – 43,997
2017 – 44,073
2018 – 47.452
A lower admit rate without change in admission criteria and preferences doesn’t inherently mean ability to estimate chances is better or worse. It just means the admission threshold has changed. A smaller portion of applicants are highly likely to be admitted, and a larger portion of applicants are highly likely to be rejected. The portion of borderline applicants for which admissions decisions are less obvious may or may not change. Rather than this degree of difference in admit rate, I’d be more concerned about year to year changes in the applicant pool and preferences.
I did not mean to suggest I can predict Stanford admissions with perfect accuracy. However, it has been my experience that admission decisions meet expectations far more often than not, rather than just a crap shoot of unpredictable after crossing a stat threshold for basic academic qualification.
I interview students for Stanford. As part of interviews, I rate students in multiple categories. I realize that these ratings and interviews in general are given little weight in the admission process, yet acceptance decisions so far have matched up almost perfectly with the median of these ratings, even among which students are deferred/waitlisted, rather than outright admitted or rejected. Stanford is one of the few highly selective colleges that defers truly borderline applicants and rejects the vast majority in the early round.
The correlation with decisions is especially surprising given how limited information I have about the applicant. I believe a large portion of this correlation relates to the interview rating categories being similar to what Stanford says they are looking for on their website and similar to some of the key more influential rating criteria/categories used by Stanford admission officers. Students who do very well in this criteria tend to be accepted, and students who do not do very well tend to be rejected. Obviously the latter group is larger than the former. It also helps to interview in a limited area, generally among the same few upper SES high schools.