Table:
|  |  | Quarter Ended |  |  |
| --- | --- | --- | --- | --- |
|  | December 31, 2019 | September 30, 2019 | June 30, 2019 | March 31, 2019 |
| Sales, net | $  338,268 | $  175,127 | $ 134,810 | $ 140,743 |
| Gross Profit | $112,295 | $73,491 | $64,126 | $65,740 |
| Restructuring Expense | $1,418 | $152 | $1,795 | $1,673 |
| Operating income | $22,202 | $9,390 | $11,005 | $11,791 |
| Income from continuing operations, net of income taxes | $  10,479 | $  7,256 | $ 23,373 | $ 15,387 |
| Loss (income) from discontinued operations, net of income taxes | $  (210) | $  375 | $ 8,324 | $ (9) |
| Net Income | $  10,269 | $  7,631 | $ 31,697 | $ 15,378 |
| Income from continuing operations attributable to noncontrolling interest | $  5 | $  10 | $ 11 | $ 8 |
| Net income attributable to Advanced Energy Industries, Inc. | $  10,264 | $  7,621 | $ 31,686 | $ 15,370 |
| Earnings (Loss) Per Share: |  |  |  |  |
| Continuing Operations: |  |  |  |  |
| Basic earnings per share | $  0.27 | $  0.19 | $ 0.61 | $ 0.40 |
| Diluted earnings per share | $  0.27 | $  0.19 | $ 0.61 | $ 0.40 |
| Discontinued Operations: |  |  |  |  |
| Basic loss per share | $  (0.01) | $  0.01 | $ 0.22 | $ — |
| Diluted loss per share | $  (0.01) | $  0.01 | $ 0.22 | $ — |
| Net Income: |  |  |  |  |
| Basic earnings per share | $  0.27 | $  0.20 | $ 0.83 | $ 0.40 |
| Diluted earnings per share | $  0.27 | $  0.20 | $ 0.82 | $ 0.40 |
Paragraphs:
ADVANCED ENERGY INDUSTRIES, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – (continued) (in thousands, except per share amounts)
NOTE 23. SUPPLEMENTAL QUARTERLY FINANCIAL DATA (UNAUDITED)
The following tables present unaudited quarterly results for each of the eight quarters in the periods ended December 31, 2019 and 2018, in thousands. We believe that all necessary adjustments have been included in the amounts stated below to present fairly such quarterly information. Due to the volatility of the industries in which our customers operate, the operating results for any quarter are not necessarily indicative of results for any subsequent period.
Question:
Why are the operating results for any quarter not necessarily indicative of results for any subsequent period?
Answer: volatility of the industries in which our customers operate