I can still recall the shock and the dismay within the planetary science community when it was revealed in the President's request for 2013 that funding for Planetary Science in the US would fall by about $300 million, or about 20%. Certainly, those of us in the community foresaw declining mission selection rates. In particular, the Mars program was expected to be deferred by removing the money which was originally to be reinvested once MSL's funding profile dropped off. Additionally, horizons for the Discovery and New Frontiers programs have been pushed out significantly and there are no flagships in the works this decade aside from the still undefined Mars 2020 Mission.
Traditionally, the NASA Research and Analysis (R&A) program has filled in the gaps between missions, preventing the cyclic loss of talent and information that occurs between flight opportunities. This was seed capital used to foster the continued training of graduate students, postdocs, professors and soft money researchers as they looked deeper into already-acquired data. Thus, the program also did good work by enhancing the science return of missions past.
But with sequestration on the horizon, the PSD is forced to play conservatively and, correspondingly selection rates for R&A proposals have plummeted to the 10% level. Where before proposals ranked as low as good (3/5) might be chosen for funding, there are reports of rankings of very good to excellent (4.5/5) being denied. The effect of this change has been documented by the Planetary Science Institute's Mark V. Sykes and you can read the testimonials here. If we look at the "budget wedge" for planetary science presented at the 2011 LPSC conference we can get a better idea of one reason why selection rates have necessarily declined:
The 2011 Fiscal Planning Wedge for the Planetary Decadal Survey. The empty white space beneath the heavy black line was thought to be the space we were planning. We were wrong. The request for 2013 nearly follows the colored bars down to below $1.2 billion forcing either no new starts or heavy reductions. We're only now finding out what that number means. Sequestration forces additional cuts.