Taxation amounts to a transfer of purchasing power to the public authority, and this relation to spending should never be forgotten when discussing the relative merits of different kinds of taxes; it is the net effect that matters. Lord Stamp has pointed out that the very great expansion of government activity in the days and the consequent high taxation have focused public attention much more both on public expenditure and on the means adopted to obtain the necessary revenue. The principle of equitable taxation has given rise to much more controversy than all the other three put together. In the first place this maxim is often a de facto justification for a tax, and equity is then defined to suit the circumstances, even in cases which have patently no other grounds than the principle of 'what the traffic will bear'.