Note C - Shareholders' Equity  | 
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| Share-based Payment Arrangement [Text Block] | 
 NOTE C – SHAREHOLDERS’ EQUITY  Share Repurchase Program:  On  November 13, 2014,  the Company announced that its Board of Directors had approved a stock repurchase program under which it will purchase up to $8,000,000  of its outstanding shares of common stock. On  April 25, 2017,  the Board of Directors increased the repurchase authorization by $4,000,000  to $12,000,000  of common stock. The program does not  obligate Clearfield to repurchase any particular amount of common stock during any period. The repurchase will be funded by cash on hand. The repurchase program is expected to continue indefinitely until the maximum dollar amount of shares has been repurchased or until the repurchase program is earlier modified, suspended or terminated by the board of directors. As of  September 30, 2019,  the Company  may  repurchase up to $5,409,326  of its outstanding shares of common stock.The Company is authorized to issue   50,000,000  shares of common stock at $.01  par value and 5,000,000  undesignated shares. From the undesignated shares, 500,000  shares have been designated as Series B Junior Participating Preferred Shares and none  of such shares have been issued or are outstanding. The Board of Directors  may,  by resolution, establish from the remaining undesignated shares different classes or series of shares and  may  fix the relative rights and preferences of shares in any class or series.Stock-Based Compensation:  The Company’s stock-based compensation plans are administered by the Compensation Committee of the Board of Directors, which selects persons to receive awards and determines the number of shares subject to each award and the terms, conditions, performance measures and other provisions of the award.The Company currently has   one  equity compensation plan, the 2007  Stock Compensation Plan, from which it grants equity awards that are used as an incentive for directors, officers, and other employees. The 2007  Stock Compensation Plan has 851,134  shares available for issue as of  September 30, 2019.  As of  September 30, 2019,  
$2,371,309  of total unrecognized compensation expense related to non-vested awards is expected to be recognized over a period of approximately 4.9  years. The Company recorded related compensation expense for the years ended  September 30, 2019,  
2018,  and 2017  of $1,729,025,  $2,003,207,  and $2,319,975,  respectively. For the year ended  September 30, 2019,  
$1,638,829  of this expense was included in selling, general and administrative expense and $90,196  was included in cost of sales. For the year ended  September 30, 2018,  
$1,835,086  of this expense was included in selling, general and administrative expense and $168,121  was included in cost of sales. For the year ended  September 30, 2017,  
$2,103,621  of this expense was included in selling, general and administrative expense and $216,354  was included in cost of sales.Stock Options:  The Company uses the Black-Scholes option pricing model to determine the weighted average fair value of options granted. During the fiscal year ended  September 30, 2019,  the Company granted employees non-qualified stock options to purchase an aggregate of 172,000  shares of common stock with a weighted average contractual term of 4  years, a three  year vesting term, and a weighted average exercise price of $12.17.  During the fiscal year ended  September 30, 2018,  the Company granted employees non-qualified stock options to purchase an aggregate of 108,000  shares of common stock with a weighted average contractual term of 4.7  years, a three  year vesting term, and a weighted average exercise price of $13.37.  There were no  stock options granted during the year ended  September 30, 2017.  The fair value was estimated at the grant date using the assumptions listed below:
 The expected stock price volatility is based on the historical volatility of the Company’s stock for a period approximating the expected life. The expected life represents the period of time that options are expected to be outstanding after their grant date. The risk-free interest rate reflects the interest rate at grant date on   zero -coupon U.S. governmental bonds having a remaining life similar to the expected option term.Options are generally granted at fair market values determined on the date of grant and vesting normally occurs over a    three  to five -year period. However, options granted to directors have a one  year vesting period and a six  year contractual term. The maximum contractual term is normally six  years. Shares issued upon exercise of a stock option are issued from the Company’s authorized but unissued shares. There were 36,000  options vested during the year ended  September 30, 2019  and no  options vested during the year ended  September 30 2018.  For the year ended  September 30, 2019,  there were 6,750  stock options that were exercised using a cashless method of exercise. For the year ended  September 30, 2018,  there were 2,250  stock options that were exercised using a cashless method of exercise. The intrinsic value of options exercised during the years ended  September 30, 2019  and  September 30, 2018  was $81,728  and $75,767,  respectively.Option transactions under the   2007  Stock Compensation Plan during the years ended  September 30, 2019  and 2018  are summarized as follows:
 The following table summarizes information concerning options exercisable under the   2007  Stock Compensation Plan:
 The following table summarizes information concerning options currently outstanding at:  
 Restricted Stock:  The Company’s 2007  Stock Compensation Plan permits our Compensation Committee to grant other stock-based awards. The Company has awarded restricted stock grants to employees that vest over one  to ten  years.Restricted stock transactions during the years ended    September 30, 2019  and 2018  are summarized as follows:
 The Company repurchased a total of   40,933  shares of our common stock at an average price of $13.51  in connection with payment of taxes upon the vesting of restricted stock previously issued to employees for the year ended  September 30, 2019.  The Company repurchased a total of 41,989  shares of our common stock at an average price of $11.66  in connection with payment of taxes upon the vesting of restricted stock previously issued to employees for the year ended  September 30, 2018. 
Employee Stock Purchase Plan:  The Clearfield, Inc. 2010  Employee Stock Purchase Plan (“ESPP”) allows participating employees to purchase shares of the Company’s common stock at a discount through payroll deductions. The ESPP is available to all employees subject to certain eligibility requirements. Terms of the ESPP provide that participating employees  may  purchase the Company’s common stock on a voluntary after tax basis. Employees  may  purchase the Company’s common stock at a price that is no  less than the lower of 85%  of the fair market value of one  share of common stock at the beginning or end of each stock purchase period or phase. The ESPP is carried out in six -month phases, with phases beginning on  July 1  and  January 1  of each calendar year. For the phases that ended on  December 31, 2018  and  June 30, 2019,  employees purchased 17,312  and 19,923  shares, respectively, at a price of $  For the phases that ended on 8.43 . December 31, 2017  and  June 30, 2018,  employees purchased 14,242  and 15,932  shares, respectively, at a price of $10.41  and $9.39  per share, respectively. As of  September 30, 2019,  the Company has withheld approximately $80,708  from employees participating in the phase that began on  July 1, 2019.  After the employee purchase on  June 30, 2019,  
49,846  shares of common stock were available for future purchase under the ESPP. | 
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