And, indeed, these costs have declined, but by less than might otherwise have been the case; much of oil development innovation outside OPEC has been directed at overcoming an increasingly inhospitable and costly exploratory environment, the consequence of more than a century of draining the more immediately accessible sources of crude oil.
BIS Review 10/2005  5  1980-1990  1991-2003  Operating profit  45.9  20.19  Net value adjustments, net non-recurring expense / income  -23.2  -8.75  Pre-tax profit rate  22.7  11.4  Taxes  -11.4  -5.4  Return on equity  11.3  6.0  Contribution to formation of the profit rate (as a percentage of capital and reserves)  6  BIS Review 10/2005