Enforced
Facilitated or monitored
Independent
40,000 returns
30,000
20,000
10,000
0
2008
2012
2016
2020
2006
2010
2014
2018
Enforced
Facilitated or monitored
Independent
40,000 returns
30,000
20,000
10,000
0
2006
2008
2010
2012
2014
2016
2018
2020