Assuming by "20111" you mean 2011.
The difference in years is 2011 and 1990 is 21 years.
In 21 years the rate of change was "-$1850" (44,450 - 6,300).
Furthermore, this can be divided by 21 to get the AVERAGE rate of change in 1 year
21 years / -1850 = -$88.096 (3 DP)
