Year	Number	Price
1973	2691	3.05
1974	2732	2.78
1975	2874	2.56
1976	2827	2.51
1977	2844	2.54
1978	2783	2.41
1979	2706	2.41
1980	2617	2.42
1981	2666	2.39
1982	2602	2.48
1983	2541	2.63
1984	2560	2.58
1985	2293	2.67
1986	2102	3.04
1987	2125	3.41
1988	2101	3.48
1989	1661	4.12
1990	1725	4.30
1991	1541	4.75