Year	Percent change (Units)
1981	30.457
1982	31.907
1983	19.469
1984	9.759
1985	11.641
1986	10.713
1987	29.196
1988	17.321
1989	10.598
1990	13.843
1991	11.725
1992	16.074
1993	8.256
1994	61.216
1995	37.311
1996	8.282
1997	4.843
1998	6.403
1999	10.105
2000	9.864
2001	5.683
2002	13.521
2003	-0.790
2004	27.327
2005	11.440
2006	10.829
2007	8.214
2008	10.141
2009	7.994
2010	10.195
2011	6.903
2012	5.778
2013	6.258
2014	6.026
2015	7.563
2016	5.952
2017	10.598
2018	6.943
2019	3.975
2020	4.569
2021	6.158
2022	10.823
2023	7.451
2024	7.704
2025	7.432
2026	7.029
2027	6.593
2028	6.148
2029	6.000