2016 started with 1211 plebes on I-Day. Lost 32 by the end of first semester plebe year, including plebe summer attrition. I don't have numbers for class size at the end of plebe summer, so I can't tell how many we lost during fall semester specifically.
My class lost 10 during second semester plebe year. Lost 13 more during first semester youngster year. 23 more second semester youngster year. Highest academic year attrition (that I have data for) was this semester, 26, which makes sense due to 2 for 7.
That adds up to 104 gone since I-Day. After 2 for 7 the class sizes tend to stay the same for the last two years. Separation usually isn't voluntary after commitment signing. I don't expect our class to lose more than a handful from here on.
Judging by the first data point alone, it looks like 2018 is at about the same place. Less candidates matriculated on I-Day, but less plebes dropped out during Plebe Summer.