Laffer curve at an intermediate rate of taxation, and then falls again to zero revenue at a 100% tax rate. However, the shape of the curve is uncertain and disputed among economists. Under some assumptions, such as revenue being a continuous function of the rate of taxation, the maximum illustrated by the Laffer curve is a result of Rolle's theorem, which is a standard result in calculus. One implication of the Laffer curve is that reducing or increasing tax rates beyond a certain point is counter-productive for raising further tax revenue. A hypothetical Laffer curve for any given economy can only be
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: