The following table shows the average nominal interest rates on six-month Treasury bills between 1986 and 1990, which determined the nominal interest rate that the U. S. government paid when it issued debt in those years. The table also shows the inflation rate for the years 1986 to 1990. (All rates are rounded to the nearest tenth of a percent.) Complete the table by calculating the real interest rates for the years 1986 to 1990.
Year
Nominal Interest Rate
Inflation Rate
Real Interest Rate
(Percent)
(Percent)
(Percent)
1986 6.0 1.9
1987 6.1 3.6
1988 6.9 4.1
1989 8.0 4.8
1990 7.5 5.4
According to the table, in which year did buyers of six-month Treasury bills receive the highest real return on their investment?

1986
1987
1988
1989
1990