Efficient diversification will not be enough to earn good returns; even very well established track records will provide a less
reliable guide to future performance; and bond managers will probably have to stray far from their comfort zone to deliver even modestly positive real returns.
The letter says that the grades obtained provide a better
guide to future performance of students as Cambridge undergraduates than other methods of selection, such as GCSE results — which are «nowhere near as
reliable» - or aptitude tests.