<p>Any attempt to determine the ease of graduation admissions in different fields is futile. Too much is subjective. Let’s take computational biology, as was discussed above. That’s a very hot field, with an accompanying demand for students since the funding levels tend to be high. Yes, there’s a lot of money in the field, but there are also a lot of students who are interested in it. If you are a molecular biology student with extensive math and computer training and solid research experience, you might find admission to top programs easy, even though your GPA was a 3.4. You may even say that there’s no reason for anyone to attend a PhD program out of the top ten because you got in everywhere you applied with only a 3.4. But if you don’t have much research, or don’t have a solid bio/math/computer combination background, you might find admissions extremely competitive, even with a 4.0. </p>
<p>Likewise, there might not be many (relatively speaking) students interested in astrophysics. Some will find admissions “easy” while others will think it “nearly impossible,” and it all depends on subtle, and sometimes not-so-subtle, aspects of the applicant’s background. </p>
<p>Just apply to the programs that promise to challenge you and that fit with your research interests. Some students may have to wait for another application cycle because they don’t get into any programs the first time, for whatever reasons.</p>