Why was the loss at Bull Run/Manassas so dangerous to the north?

How do economists measure the success, or shortcomings, of the economy?

Say a certain manufacturing industry has 63.1 thousand jobs in 2008, but is expected to decline at an average annual rate of 1.7 thousand jobs per year from 2008 to 2018. assuming this holds true, what will be this industry’s percent change from 2008 to 2018? a. 70% b. -27% c. -17% d. -75%

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