Dear TimetoFocus,
Thanks for your post.
You raise an interesting point about the trends regarding a candidate's age and b-school. Unfortunately, I don't think there's a definitive answer here in terms of whether it's purely the schools that are driving this or more of a shift in the age of the typical applicant in the pool, but my general opinion is that it is mostly the former.
Having said that, let me make a few points to help illuminate where things presently stand:
1) It is true that many of the leading MBA programs have made concerted efforts to 'get younger'. Schools like Stanford, HBS, Wharton and others have increased their presence on undergraduate campuses across the US in hopes of 'planting the seed' with college students and encouraging them to consider the MBA. In some cases this means applying directly from college (Stanford waives the application fee for any college senior that applies) and in other cases it merely means letting applicants know that they needn't work 4-5 years before applying, and that 1-2 years may very well be sufficient. HBS has even introduced their 2+2 Program for rising college seniors in an effort to 'lock in' the best and brightest and get a step ahead of their peer schools in the admissions food chain.
2) There are many reasons that the schools are looking at younger applicants, and they do not all relate to percentage increase in wage post-MBA (as you seemed to suggest). For example, in some cases, it's merely an effort to attract top students who may be turned off by the long wait for business school (if 4+ years of experience is required) and might otherwise shift their focus to PhDs, MDs or JDs instead of telling mom and dad that they merely "plan to work for a few years" after college. In other cases, it's the fact that younger students tend to perform better academically in b-school and that older applicants often have an overly utilitarian approach to b-school ("I'm only here to get a job and increase my wage"). I've also heard admissions officers and career services staff voice concerns about how it can be "hard to teach an old dog new tricks" or to convince an investment bank to hire a 34 year old into an Associate position where they are expected to be worked to the bone alongside 28 year-olds. Finally, and perhaps more importantly, some leading business schools believe that younger students are more likely to have a 'transformational' experience in b-school - resulting in greater loyalty to the program (and ultimately stronger alumni giving).
Of course, despite this push for younger applicants, most of the leading MBA programs are still looking at average ages of 27-29 years old upon matriculation. In addtion, these programs (and their professors) do value the experience that students bring to the classroom. Schools like Kellogg and Tuck have been particularly vocal about their preference for experienced students in the classroom.
So what does this all mean for you? If you are going to be 31 when you apply next year, my first question would be why aren't you considering a R2 application this year? You are already a bit of an outlier in the age category, so I'm wondering why you've decided to wait. Having said that, I don't think that admission to b-school at age 31 is impossible by any stretch. You will merely need to be tuned into the potential concerns admissions officers have about older applicants and do a highly effective job of presenting yourself in the admissions process.
Best of luck,
Graham