Year	% of revenue
2013	2.943997005810693
2014	2.3605030945239185
2015	2.4397783960326627
2016	2.1255113951049216
2017	1.8664702355995895
2018	1.8058954863960734
2019	1.6528160365429565
2020	1.6644131094396497