In such cases, well-planned design of the tax instrument over a number of years can ensure that revenue increases substantially or at least remains stable over time - for example, by introducing a gradual increase in tax rates (a tax escalator) to compensate for gradually falling consumption as economic actors respond to the price signal created by the tax. This is particularly important in developing countries, where government budgets are limited and tend to be vulnerable to price shocks. In China, for example, differentiated grid prices for desulfurized electricity had a clearly defined objective of driving the desulfurization of coal generation (see Section 5.7).