Answer: 30% change in the number of unemployed construction workers over this period
Explanation:
September 1, 1992
The total number of construction workers = 1,000 (assume);
16% are unemployed, so the number of unemployed workers is 16*1000/100= 160.
September 1, 1996
The total number of construction workers 20% greater 20*1000/100+1000=1200;
9% are unemployed, thus the number of unemployed workers = 9*1200/100=108.
Decrease is 52, which is approximately 30% of 160.