Table 2. WTPs as a percentage of GDP and net national income: the results of meta-analysis of the included studies.

Variable	Method	Pooled estimate	95% confidence interval	P-value	N of studies [ref]
WTP household (% GDP per capita)	Fixed effect	1.82	1.5–2.15	0.000	4 [16, 19, 21, 29]
WTP Household (% net national income per capita)	Fixed effect	2.16	1.83–2.50	0.000	4 [16, 19, 21, 29]
WTP of individual (% GDP per capita)	fixed effect	1.18	1.13–1.24	.0.000	10 [16, 17, 22, 27–30, 32–34]
WTP of individual (% net national income per capita)	fixed effect	1.39	1.34–1.44	0.000	10 [16, 17, 22, 27–30, 32–34]