In some countries these goods are (partially) provided by the state blurring the concept of the "market price" implicitly used in setting the monetary poverty line. It makes a big difference whether water, sanitation, health and education have to be paid by households "at competitive market prices" or at prevailing prices that may or may not be reduced by public subsidies. The application of Rowntree's definition may be relatively straightforward for "food, shelter and clothing" but much more difficult for "other necessities" such as water, sanitation, health and education for which markets may be missing or incomplete (see also Thorbecke, 2008; Bourguignon and Chakravarty, 2003; Tsui, 2002). Equivalence scales are widely - but not always - used and often disputed.