Instead of deploying their margin advantage as a defence of mutuality, around 1980 building societies began setting mortgage rates with reference to market clearing levels. In sum they began behaving more like banks, seeking to maximise profit instead of the advantages of a mutual organisation. Thus, according to the Bank of England's Boxall and Gallagher (1997), "... there was virtually no difference between banks and building society 'listed' interest rates for home finance mortgage lending between 1984 and 1997. This behaviour resulted in a return on assets for building societies which was at least as high as Plc banks and, in the absence of distribution, led to rapid accumulation of reserves". As Boxall and Gallagher (1997) also observe; "... accumulation of reserves in the early-1990s, beyond regulatory and future growth requirements, is difficult to reconcile with conventional theories of mutual behaviour".