It’s useful to look at a sampling of the stats of accepted and rejected applicants.
For Yale class of 2018
http://talk.collegeconfidential.com/yale-university/1629434-official-yale-class-of-2018-rd-results-thread.html
For Harvard class of 2018
http://talk.collegeconfidential.com/harvard-university/1627558-official-harvard-university-2018-rd-decisions-only.html
For Brown class of 2018
http://talk.collegeconfidential.com/brown-university/1630860-official-brown-class-of-2018-rd-results-only.html
For Princeton class of 2018
http://talk.collegeconfidential.com/princeton-university/1631203-princeton-2018-rd-results-discussion-and-review-p1.html
For Columbia class of 2018
http://talk.collegeconfidential.com/columbia-university/1630972-official-columbia-university-class-of-2018-rd-results-only-p1.html
For University of Pennsylvania class of 2018
http://talk.collegeconfidential.com/university-pennsylvania/1629369-official-penn-class-of-2018-rd-results-only-thread-p1.html
For Dartmouth class of 2018
http://talk.collegeconfidential.com/dartmouth-college/1623261-dartmouth-class-of-2018-regular-decision-results.html
For Cornell class of 2018
http://talk.collegeconfidential.com/cornell-university/1621180-official-cornell-regular-decision-results-class-of-2018-p4.html