To compute Inventory Turnover: Cost of Goods Sold/ Average Inventory

Why the average of 2 years, not 3 years? Why current year average inventory equal to the current year + 1 year ago, but not the average of 3 years?

2 Yrs Ago SIMON COMPANY Comparative Balance Sheets December 31 Current Yr 1 Yr Ago Assets Cash $31,800 $35,625 Accounts receivable, net 89,500 62,500 Merchandise inventory 112,500 82,500 Prepaid expenses 10,700 9,375 Plant assets, net 278,500 255,000 Total assets $523,000 $445,000 SIMON COMPANY Income Statements Current Yr 1 Yr Ago Sales $673,500 $532,000 Cost of goods sold 411,225 345,500 Other operating expenses 209,550 134,980 Interest expense 12,100 13,300 Income tax expense 9,525 8,845 Total costs and expenses 642,400 502.625 Net income $31,100 $29,375 $37,800 50,200 54,000 5,000 230,500 $377,500 Earnings per share $1.90 $1.80 Liabilities and Equity Accounts payable Long-term notes payable $129,900 98,500 $75,250 101,500 $51.250 83,500 Common stock, $10 par value Retained earnings Total liabilities and equity 163,500 131, 100 $523,000 163,500 104,750 $445,000 163,500 79,250 $377,500 (2) Compute inventory turnover. Inventory Turnover Inventory Turnover Cost of Goods Sold / Average Inventory Current Year $411,225 / ($112,500 + $82,500)/2 $411,225 / $97,500 1 Year Ago $345,500 / ($82,500 + $54,000)/2 $345,500 / $68,250 4.2 times