Steve Hsu has a recent posting Survivor: theoretical physics, which links to data about the theoretical particle physics job market compiled by Erich Poppitz from listings on the Theoretical Particle Physics Rumor Mill web-site.
Back in 2001-2 I also spent some time looking at this data, and estimated that in recent years there had been typically about 15 tenure-track hires each year in particle theory, of which roughly half were going to string theorists. Starting around 2000, the number of hires started to increase, as it has increased throughout academia during a period of reasonably healthy university budgets and an increasing number of retirements (of those hired during the 60s when many universities expanded dramatically). Since 2000 the number of hires has typically been more like 20, anomalously high at 28 in 2007. The anomalously low number of 15 for this past year’s hiring may be a fluctuation, but it also may be an indication of either university budget cutbacks or increasing unpopularity of particle physics in US physics departments. The fraction of string theory hires has gone down dramatically, to more like 25% over the last 5 years.
I don’t have any data at hand about the recent total number of people getting particle physics Ph.D.s, and whether this number has grown with the number of faculty hires. I did find at one point a number of 78 for particle theory Ph.D.s in 1997, but I don’t know if this included degrees in cosmology, which increasingly has become mixed with particle theory. Poppitz also lists numbers of hires by institution. Princeton comes out significantly ahead with 23 people getting jobs over 15 years. I’d guess there are typically about 3-4 people/year getting theory Ph.D.s there. So, traditionally, if you want to maximize your chance at a job, Princeton is the place to go. Not clear how this will work out in the future, given the very small number of string theorists getting hired.
To get some idea of the imbalance between Ph.D.s being produced and tenure-track jobs, in 2007 one institution, Harvard, produced 8 theory Ph.D.s. That’s more than half the total number of tenure-track hires this past year. In the past a large number of these Ph.D.s ended up working in finance, but prospects in that industry are not looking so good either.