<p>To be honest, I am only familiar with biomedical graduate programs, which is what I am interested in.</p>
<p>Most of these programs accept a lower percentage of qualified internationals due to funding limitations (I believe this is due to NIH restrictions). I quote:</p>
<p>The financial resources we have available to pay for students who are neither U.S. Citizens nor U.S. Permanent Residents, however, is very limited. As a result, we are able to admit only about 5-7% of our international applicant pool, and students should take this into consideration before applying to the Program.
[FAQ</a> > Biological & Biomedical Sciences | Yale University](<a href=“http://bbs.yale.edu/apply/faq.aspx]FAQ”>Frequently Asked Questions < Biological & Biomedical Sciences)</p>
<p>We are very much interested in attracting talented students from other countries to our program. However, there are some practical issues that you should be aware of before applying. We have a limited ability to support students who are not citizens or permanent residents of the United States. Our training program is funded by a training grant from the United States government. This grant will only support US citizens or permanent residents. Only very rarely do we have funds that can be used to support citizens of other countries.
[Johns</a> Hopkin University | School of Medicine Immunology Graduate](<a href=“http://gradimmunology.med.som.jhmi.edu/how/requirements.html]Johns”>http://gradimmunology.med.som.jhmi.edu/how/requirements.html)</p>
<p>These are just two examples, but the case is similar for other biomedical programs. The exceptions are some that have large private funding, such as Rockefeller University.</p>