> What is meant by "average stock" in efficiency ratios?

What is meant by "average stock" in efficiency ratios?

Posted at: 2014-12-05 
The average value of a stock over an accounting period:

One calculates the average value of stock by adding the stock value at the beginning of an accounting period to the value at the end ,and dividing by two.

http://financial-dictionary.thefreedicti... .

The formula for the efficiency stock is:

cost of goods sold/average stock

I know what the "cost of goods sold" is, but what does "average stock" mean? It's not mentioned anywhere else in my textbook. Also, where is it indicated on a balance sheet?

Thank you!