Year	Percent change (Units)
1980	22.051
1981	11.236
1982	4.855
1983	5.637
1984	8.622
1985	-3.277
1986	12.859
1987	14.137
1988	29.703
1989	9.888
1990	13.077
1991	8.587
1992	7.243
1993	16.977
1994	18.492
1995	21.087
1996	9.346
1997	10.231
1998	-4.417
1999	8.018
2000	14.328
2001	-3.641
2002	7.381
2003	13.871
2004	19.399
2005	12.780
2006	10.954
2007	8.538
2008	5.261
2009	-7.204
2010	17.788
2011	7.691
2012	1.397
2013	6.140
2014	3.620
2015	4.968
2016	0.046
2017	7.528
2018	8.261
2019	-0.025
2020	-0.179
2021	9.202
2022	3.003
2023	2.384
2024	7.989
2025	4.624
2026	4.148
2027	3.817
2028	2.370
2029	2.291