Year	Percent change (Units)
1987	7.306
1988	10.451
1989	9.148
1990	4.999
1991	9.129
1992	-3.095
1993	5.222
1994	6.711
1995	4.235
1996	5.387
1997	12.605
1998	11.812
1999	14.816
2000	15.012
2001	6.830
2002	-1.489
2003	3.644
2004	9.095
2005	6.148
2006	11.492
2007	2.564
2008	2.181
2009	-9.073
2010	14.253
2011	6.746
2012	1.760
2013	6.229
2014	8.236
2015	5.707
2016	3.752
2017	0.754
2018	3.711
2019	7.411
2020	-0.377
2021	12.374
2022	-1.906
2023	-0.139
2024	1.536
2025	2.600
2026	2.500
2027	2.500
2028	2.500
2029	2.500