Year	2017 PPP (%)
1977	45.6
1983	41.4
1987	37.8
1993	35.9
2004	31.5
2009	27.5
2011	21.2
2015	19.1
2016	18.7
2017	15.7
2018	13.1
2019	13.4
2020	15.2
2021	13.3