Have there been any recent studies on the effect of age on PhD success rates in the US?

Question

I think the title is fairly self-explanatory. I am wondering if any recent studies (past 20 years or so) have been published that look at possible correlations between age and the 'success rate' of PhD candidates? I understand that 'success rate' may be somewhat subjective - I'm thinking of possible metrics such as dropout rate, years to completion, no. of papers published, impact factor 5 years after graduation.

The background to this is that I am 37 and planning to apply to Engineering PhD programs in my area this Fall. However, I had a casual conversation with someone recently who is connected to one of those schools, who commented that there might be some thinking on the part of an admissions committee that I may be 'past my peak' for their PhD program (they weren't representing it as their own personal view). However, this seems at odds with what I have read online and advice I have received from a couple of Professors that I know (not related to these schools), which indicates that more mature PhD candidates tend to do well and are quite highly regarded.

Now, I'm not trying to point fingers or accuse anyone of ageism here. For all I know, my contact's suspicion might be mistaken, or I may have misinterpreted. But, it occurs to me that it would be great if I could point to some hard data that makes a persuasive case that mature PhD candidates on average perform at least as well as fresh graduates, which might help to pre-emptively 'head off' any doubts regarding my age.

Answer 1

I don't have exact references handy right now, but a researcher at UC Davis named Dean Simonton did some work on academic and creative output and age. The upshot is that up until actual senescence--so certainly no younger than around 70 for neurologically healthy adults--the relevant variable is "career age" (the time one has been working in a particular field) and not biological age.

Answer 2

I have never heard of any PhD programs that require age/DoB etc as part of the application. Age is not a problem, however there are many problems indirectly related to age.

• Letters of recommendations (LoRs). This is one of the most important part of the application. The strength of the LoR depends on who write it, and what they write. It is much much easier if you just worked with (well-known) professors, and they can write good things about you. 20+ years after graduation, obtaining good LoRs can be a huge challenge.
• Statement of purpose (SoP). A good SoP needs to show your background, and passions about the field. Your research interest cannot be too broad (but not too narrow either). It's not easy if you have worked in industry for years, which is often not related to academic research.
• Research potential. That's also what you need to show in your SoP. If you have no research experience, it is easier to have an excuse when you just graduate, than when you have worked a routine job for 20+ years.
• As there is US-tag, most PhD programs require GRE score. That means you need to memorize more than 3000+ words that are rarely used in everyday life. If you have a family, kids to take care of, finding a time to study them can be a huge problem.
• Living expense. After many years working in industry, people are often in a senior level, that PhD stipend is just a tiny fraction of their salary in industry. It's hard to downgrade, in particular when you have a family to support.

For those reasons, you will not see many old PhD students. If somebody wants to conduct such a studies, it is extremely hard to find enough samples.

In summary, if you have good LoRs, good background, good GRE, good stories (research experience) to tell in SoP, go ahead and apply, nobody will care about your age. There are challenges with age, but age discrimination is illegal in the US and is unlikely one of them.