Year	Percent change (Units)
1980	19.629
1981	12.214
1982	12.416
1983	17.549
1984	10.812
1985	13.241
1986	18.152
1987	11.634
1988	11.585
1989	14.843
1990	11.466
1991	17.857
1992	17.047
1993	13.768
1994	7.250
1995	9.962
1996	9.058
1997	8.550
1998	7.775
1999	8.644
2000	6.131
2001	6.919
2002	12.562
2003	7.166
2004	5.023
2005	3.438
2006	6.073
2007	8.012
2008	10.715
2009	7.380
2010	3.495
2011	5.037
2012	6.051
2013	4.865
2014	5.370
2015	3.218
2016	6.597
2017	4.448
2018	4.752
2019	5.187
2020	4.978
2021	6.048
2022	8.272
2023	6.343
2024	6.384
2025	5.352
2026	5.426
2027	5.103
2028	5.001
2029	5.000