Optimal tax tax rates are lowered, revenue will be decrease by the same amount—and an economic effect—which provides incentives for individuals to increase their work output through low tax rates. These correspond to the mechanical and behavioural effects discussed by Saez. The Laffer Curve illustrates that, for sufficiently high tax levels, the (negative) behavioural effect will outweigh the (positive) mechanical effect of a tax increase, and so increasing tax rates will reduce tax revenue. In fact, tax revenue with a tax rate of 100% is likely to be 0, since there is no remaining incentive to work at all. Therefore, the tax
From each according to his ability, to each according to his needs in solidum is that 'everyone assumes responsibility for anyone who cannot pay his debt, and he is conversely responsible for everyone else'. James Furner then argues: 'If x = a disadvantage, and y = action to redress that disadvantage, the principle of solidarity is: if any member of a group acquires x, each member has a duty to perform y (if they can assist). All we then need to add, to get to the fundamental principle of developed communism, is to assume that non-satisfaction of a need is a disadvantage. The corresponding principle of solidarity in respect of need says: