是不是真的会发生这种事呢，自发性消费可能减少吗，绝对意义上的。篮坛日暖29说 只要存钱就可以，可是用于自发性消费的钱也可以存起来吗？ 还是不理解 请大家指教 谢谢

我也不太明白了，楼主,希望斑主能详细解释一下. 为什么可能是负数呢?

MPC=dC/dY,for this formula, use the Mathematical way to exaplain the MPC function is expressed as the derivative of the consumption (C) function with respect to disposable income (Y). in the other word, MPC is measured as the ratio of the change in consumption to the change in income, thus giving us a figure between 0 and 1 under the condition if the subject did not borrowed money to finance expenditures higher than their income.

on the other hand, because one minus the MPC equals the MPS. in this case, we can not conclude that MPC<0.