We are required to estimate the cost of certain forms of share-based compensation, including employee stock options, restricted stock units and our employee stock purchase plan, and to record a commensurate expense in our income statement.  Share-based compensation expense is a non-cash expense that varies in amount from period to period and is affected by the price of our stock at the date of grant.  The price of our stock is affected by market forces that are difficult to predict and are not within the control of management.  Our other non-GAAP adjustments (except as related to non-GAAP net sales) are either non-cash expenses, unusual or infrequent items or other expenses related to transactions.  Management excludes all of these items from its internal operating forecasts and models.

We are using non-GAAP net sales, non-GAAP gross profit, non-GAAP gross profit percentage, non-GAAP operating expenses in dollars and as a percentage of sales including non-GAAP research and development expenses and non-GAAP selling, general and administrative expenses, non-GAAP operating income, non-GAAP other expense, net, non-GAAP income tax rate, non-GAAP net income, and non-GAAP diluted earnings per share which exclude the items noted above, as applicable, to permit additional analysis of our performance.

Management believes these non-GAAP measures are useful to investors because they enhance the understanding of our historical financial performance and comparability between periods.  Many of our investors have requested that we disclose this non-GAAP information, including the effect of changes in distributor inventory holdings, because they believe it is useful in understanding our performance as it excludes non-cash and other charges that many investors feel may obscure our underlying operating results and provides better information regarding end-market demand for our products.  Management uses these non-GAAP measures to manage and assess the profitability of our business and for compensation purposes.  We also use our non-GAAP results when developing and monitoring our budgets and spending.  Our determination of the above non-GAAP measures might not be the same as similarly titled measures used by other companies, and it should not be construed as a substitute for amounts determined in accordance with GAAP.  There are limitations associated with using non-GAAP measures, including that they exclude financial information that some may consider important in evaluating our performance.  Management compensates for this by presenting information on both a GAAP and non-GAAP basis for investors and providing reconciliations of the GAAP and non-GAAP results.

²  Generally, gross margin fluctuates over time, driven primarily by the mix of microcontrollers, mixed-signal products, analog products and memory products sold and licensing revenue; variances in manufacturing yields; fixed cost absorption; wafer fab loading levels; costs of wafers from foundries; inventory reserves; pricing pressures in our non-proprietary product lines; and competitive and economic conditions.  Operating expenses fluctuate over time, primarily due to net sales and profit levels.

³  Diluted Common Shares Outstanding can vary for, among other things, the trading price of our common stock, the exercise of options or vesting of restricted stock units, the potential for incremental dilutive shares from our convertible debentures (additional information regarding our share count is available in the investor relations section of our website under the heading "Supplemental Financial Information"), and repurchases or issuances of shares of our common stock.  The diluted common shares outstanding presented in the guidance table above assumes an average Microchip stock price in the December 2018 quarter between $65.00 and $75.00 per share (however, we make no prediction as to what our actual share price will be for such period or any other period and we cannot estimate what our stock option exercise activity will be during the quarter).