Year	Percent change (Units)
1980	19.190
1981	12.000
1982	9.524
1983	13.768
1984	19.745
1985	10.638
1986	14.183
1987	25.053
1988	33.838
1989	12.453
1990	11.857
1991	8.227
1992	23.236
1993	22.775
1994	34.659
1995	83.148
1996	37.733
1997	9.137
1998	29.779
1999	44.759
2000	29.597
2001	22.700
2002	14.745
2003	9.577
2004	11.424
2005	15.466
2006	13.918
2007	7.942
2008	8.716
2009	8.416
2010	7.409
2011	7.621
2012	21.296
2013	28.279
2014	23.775
2015	21.860
2016	21.727
2017	11.541
2018	9.215
2019	9.378
2020	8.639
2021	9.343
2022	20.839
2023	30.295
2024	27.892
2025	14.725
2026	8.123
2027	6.786
2028	6.487
2029	6.504