T-Bills
1950 to 1959	Average		2.0	%
1960 to 1969	Average		4.0
1970 to 1979	Average		6.3
1980 to 1989	Average		8.9
1990 to 1999	Average		4.9
2000 to 2009	Average		2.8

Table 9.4 Annual Standard Deviation for T-Bills

	T-Bills
1950 to 1959		0.8	%
1960 to 1969		1.3
1970 to 1979		1.8
1980 to 1989		2.6
1990 to 1999		1.2
2000 to 2009		1.9

Use the tables above to calculate the coefficient of variation of the risk-return relationship in T-bills during each decade since 1950.