Year	Percent change (Units)
1991	6.127
1992	5.966
1993	4.502
1994	4.151
1995	3.555
1996	2.317
1997	1.813
1998	1.699
1999	3.168
2000	2.535
2001	2.747
2002	2.828
2003	2.079
2004	5.041
2005	6.028
2006	12.027
2007	11.253
2008	8.804
2009	0.200
2010	1.722
2011	0.156
2012	0.601
2013	1.443
2014	3.108
2015	3.596
2016	1.619
2017	1.966
2018	3.071
2019	-1.934
2020	-2.076
2021	-0.113
2022	4.827
2023	1.623
2024	2.100
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000