Table 3. Determinants of WTP for Fecal Sludge Emptying Services, Which Were Statistically Significant (at 5% Level) in One or More Studies.

determinant of WTP	WTPa	description	reported by
economic situation category
income/expenditure	+	higher WTP for manual and mechanical emptying as customers’ income or expenditure gets higher	Harder et al.46
			Naing et al.43
			Peletz et al.10
			Ross and Pinfold49
			Vásquez and Alicea-Planas47
price	–	lower WTP for vacuum/manual emptying as prices get higher	Burt et al.44
			Harper et al.41
flat fee	–	lower WTP for vacuum truck emptying if a flat fee is used	Burt et al.44
urgency category
shared latrine	+	higher WTP for manual emptying if their latrine is shared	Peletz et al.10
household size	+	higher WTP for excreta disposal as the household size gets larger	Vásquez and Alicea-Planas47
waiting time	–	lower WTP for longer waiting time	Naing et al.43
			Harper et al.41
service characteristics category
branded service that provides workers with protection	+	higher WTP for branded vacuum truck emptying	Burt et al.44
smell prevention during work	+	higher WTP for manual emptying that prevents smell	Harper et al.41
			Jenkins et al.7
sludge taken away	+	higher WTP for vacuum truck/manual emptying that takes sludge away to a remote place	Burt et al.44
			Jenkins et al.7
sludge treatment before disposal	+	higher WTP for vacuum truck emptying that treats sludge before disposal (removing smells and pathogens)	Burt et al.44
contact with sludge prevented	+	higher WTP for pit emptying that prevents workers from contacting with sludge	Harper et al.41
fertilizer production	+	higher WTP for pit emptying that produces fertilizer from the sludge	Harper et al.41
service accessibility category
alternative hygienic method available	–	lower WTP for formal manual emptying if an alternative hygienic emptying method is locally available	Jenkins et al.7
distance from a road	–	lower WTP for vacuum truck emptying if they have a toilet located >50 m from a road	Peletz et al.10
knowledge category
knowledge about another hygienic method	–	lower WTP for manual emptying if they know another hygienic emptying method	Jenkins et al.7
knowledge about the only available option	+	higher WTP for manual emptying if they have emptied their latrine using the only available option before	Jenkins et al.7
others
education	+–	WTP for manual emptying can get higher or lower if they are more educated	Jenkins et al.7
			Peletz et al.10
			Harper et al.41
age	–	lower WTP for manual/mechanical emptying as they get older	Peletz et al.10
gender	male, +	higher WTP for manual/mechanical emptying if they are male	Peletz et al.10
province	+–	WTP vary depending on province	Harper et al.41

^aA plus sign (+) means that WTP increases as the determinant increases or the service/customer has the characteristic. A minus sign (−) means that WTP decreases as the determinant increases or the service/customer has the characteristic. Plus and minus signs (+−) mean that the determinant can either increase or decrease WTP.