The Joint Council for Qualifications have required all GCSE subjects to grade A* differently in future. OFQUAL have required all the exam Boards to return to the level of awards as made in 2008, leading to a reduction in the pass rate at all grades.
I don't have information for all subjects, but apparently in some subjects the difference is massive. In 2011 in AQA Biology 23% of all entries were graded A. In the Jan 2012 Biology module, just 0.9% of papers were graded A!
I approve wholeheartedly of the revised exam board policy of reserving A* for truly exceptional - and statisticallly rare - performance.