23 Categories for the source of drinking water comprise surface water source, unimproved water source other than surface water, and improved water source. Surface water categories include river, stream, pond, lake, and dam. Additional categories canal and irrigation channel were added in 2008. Improved water source is a source of water suitable for drinking (KNBS and ICF Macro 2010). It includes water piped into the dwelling or plot, public tap or standpipe, and rainwater. Additionally, it comprises covered well in the plot and covered public well in 2003 and tube well or borehole and protected well in 2008. Water sources that do not fall into surface or improved water categories are classified as unimproved water source other than surface water. In 2008, these are unprotected well, protected and unprotected spring, tanker truck, cart with small tank, bottled water, and "other" source.<sup>15</sup> In 2003, unimproved water category consists of open well in the plot, open public well, spring, bottled water, and "other" source.

Variables on sanitation facility comprise no sanitation, unimproved sanitation facility, and improved sanitation facility. Improved sanitation facility is defined as a toilet that is used by members of one household only and that separates excreta from human contact (KNBS and ICF Macro 2010). This includes flush toilet and ventilated improved pit (VIP) latrine; both of them not shared with other households.<sup>16</sup> The unimproved sanitation facility comprises flush toilet and VIP latrine both shared with other households, and "other" toilet. Further facilities falling into this category are pit latrine with or without slab, composting toilet, bucket toilet, and hanging toilet in 2008, and traditional pit toilet in 2003.<sup>17</sup> 15 Although protected spring is generally considered improved water source, DHS 2003 does not distinguish between protected and unprotected springs. In order to have time-consistent water source categories, we categorize both protected and unprotected springs as an unimproved water source in 2008. According to the Kenya DHS report 2008, 8% of households use protected spring and 5.6% use unprotected spring for drinking water (KNBS and ICF Macro 2010).

16 DHS 2008 defines flush toilets connected to other than piped sewer system, septic tank or pit latrine as unimproved. In 2003, information on where the flush toilet is connected to is not available. In order to have timeconsistent sanitation categories, we consider all flush toilets in 2008 improved. Only 1% of households in 2008 has a flush toilet connected to other than piped sewer system, septic tank or pit latrine (KNBS and ICF Macro 2010). 17 Although pit latrine with slab that is not shared is generally considered improved sanitation facility, DHS 2003 does not distinguish between pit latrines with and without slab. In order to have time-consistent sanitation categories, we categorize all pit latrines as unimproved sanitation in 2008. According to the Kenya DHS report 2008, 7.8% of households use a not shared pit latrine with slab and 37.9% use pit latrine without slab. Information on shared pit latrines with slab was not published (KNBS and ICF Macro 2010).