Just was playing around with this converter, to see what sort of raw marks you needed in order to get a certain UMS mark and I was shocked to see how much they vary from one exam series to the next. For example Core 4 in January 2011, you needed 61 raw marks to get 80 UMS, 68 raw marks to get 90 UMS and full marks to get 100 UMS. In contrast the same unit Core 4 in June 2011 required 51 raw marks to get 80 UMS, 58 raw marks to get 90 UMS and just 65 raw marks to get 100 UMS. I mean really do the exam papers differ that much for the grade boundaries to be so different?
From GCSE to A level, it's all changing