just to clear up some of the factual innaccuracies in this thread...
This is a gross misinterpretation and misrepresentation of what the data in the NRMP reports actually represents. US-IMGs are not broken down into seniors vs grads. The big Caribbean schools have first time placement rates of new grads, what most people call "match rate," of 80-90% (granted this doesn't include those lost to attrition prior to graduation). If you look at the ECFMG Charting Outcomes document using 2013 data, you can clearly see that the average time since graduation for unmatched US-IMGs is ~6 years. The majority of these unmatched people aren't fresh grads, they are repeat applicants. This is because there is a subset (5-10%) of caribbean grads that manage to graduate but are poor applicants (step failures, semester failures, etc) and can't match, and end up applying year after year. These people build up over time and skew the percentages in the NRMP reports. If you want to include these people when discussing "chances in the match" then you also have to include all the people from the previous 6 years that did match, otherwise you are way oversampling the yearly unmatched cohort.
Again, lots of this is just horribly untrue. Looking at the SOAP data from 2016,
USMD seniors: 2199 eligible, 635 positions accepted = 29% success rate
USMD previous grads: 995 eligible, 51 positions accepted = 5% success rate
DOs: 817 eligible, 132 positions accepted = 16% success rate
US-IMGs: 4020 eligible, 92 positions accepted = 2% success rate
foreign-IMGs: 5871 eligible, 78 positions accepted = 1% success rate
So firstly, the overwhelming majority of folks in the SOAP are not from offshore schools, 29% are. 29% are AMGs (USMD + DO) and 42% are foreign-IMGs. Secondly, no one does that well in the SOAP. There are more than a "few" AMGs in the SOAP, and the vast majority of them don't get positions. Yes, the success rates are better than for IMGs, but they still aren't very good.