In 1980 , the number of high school dropouts in a country was 5212 thousand. By 2009 , this number had decreased to 3120 thousand. Find and interpret the average rate of change per year in the number of high school dropouts.

Step 1 ：Given that the number of high school dropouts in a country was 5212 thousand in 1980 and this number had decreased to 3120 thousand by 2009.

Step 2 ：We are asked to find the average rate of change per year in the number of high school dropouts.

Step 3 ：The average rate of change is calculated by subtracting the final value from the initial value and then dividing by the change in time.

Step 4 ：In this case, the initial value is the number of high school dropouts in 1980, the final value is the number of high school dropouts in 2009, and the change in time is the number of years from 1980 to 2009.

Step 5 ：Substitute the given values into the formula: \(\frac{final\_value - initial\_value}{change\_in\_time}\)

Step 6 ：Substitute the given values into the formula: \(\frac{3120 - 5212}{29}\)

Step 7 ：Solve the equation to get the average rate of change: -72.13793103448276

Step 8 ：The average rate of change is negative, which means the number of high school dropouts decreased over the time period.

Step 9 ：The value of the average rate of change is approximately -72.14, which means that on average, the number of high school dropouts decreased by about 72.14 thousand each year from 1980 to 2009.

Step 10 ：Final Answer: The average rate of change in the number of high school dropouts per year from 1980 to 2009 is approximately \(\boxed{-72.14}\) thousand.