The gap between the richest and poorest urban quintile is at least 18 percentage points in half of the countries assessed, and in one-quarter of the countries it is 35 points or higher. This may be due in part to the fact that access to water and sanitation facilities helps determine a household's value on the wealth index that we use; see the Annex for further discussion of this matter. In half of the countries analysed, children in the poorest quintile are at least twice as likely to die before their fifth birthday as their richest urban peers. The relative disparity is even more pronounced for stunting, where prevalence in the poorest urban quintile is at least twice as high as for peers in the richest quintile in approximately 8 out of 10 of the countries analysed, and at least four times higher in 2 out of 10 countries. For both stunting and under-five mortality, relative inequality is higher in urban areas than in rural areas - a pattern opposite to that of the other indicators.