Year	Measure
1800	930.8
1820	930.8
1950	1399
1970	3121
1971	3241
1972	3291
1973	3309
1974	3462
1975	3573
1976	4186
1977	4507
1978	4774
1979	4830
1980	4492
1981	4543
1982	4616
1983	4810
1984	5069
1985	5368
1986	6167
1987	6225
1988	6987
1989	7376
1990	7477
1991	7415
1992	7855
1993	7785
1994	7842
1995	7852
1996	8318
1997	8220
1998	8670
1999	8793
2000	8676
2001	8124
2002	8269
2003	8530
2004	8878
2005	9279
2006	10060
2007	10160
2008	10630
2009	10610
2010	10570
2011	10650
2012	10540
2013	10590
2014	10760
2015	10950
2016	11170
2017	11360
2018	11550