The poorest people in the world are paying many times more than their richer compatriots for the water they need to live, and are getting more than their share of deadly diseases because supplies are dangerously contaminated, an international panel of experts concluded this week. The reason may be that the price of water is kept artificially low by government subsidies, making the water systems inefficient and unprofitable. The report was published by the World Commission on Water for the 21st Century, which is supported by United Nations agencies, a number of governments and the Ford Foundation.