pre_text: (13) (Loss) Earnings Per Common Share Basic and diluted (loss) earnings per common share for the years ended December 31, 2019, 2018 and 2017 were calculated as follows: (1) For the year ended December 31, 2019 and December 31, 2018, we excluded from the calculation of diluted loss per share 3.0 million shares and 4.6 million shares, respectively, potentially issuable under incentive compensation plans or convertible securities, as their effect, if included, would have been anti-dilutive. Our calculation of diluted (loss) earnings per common share excludes shares of common stock that are issuable upon exercise of stock options when the exercise price is greater than the average market price of our common stock. We also exclude unvested restricted stock awards that are antidilutive as a result of unrecognized compensation cost. Such shares were 6.8 million, 2.7 million and 4.7 million for 2019, 2018 and 2017, respectively.
table: Years Ended December, 31
table: 2019 2018 2017
table: (Dollars in millions, except per share amounts, shares in thousands)
table: Loss income (Numerator):
table: Net (loss) income $(5,269) (1,733) 1,389
table: Net (loss) income applicable to common stock for computing basic earnings per common share (5,269) (1,733) 1,389
table: Net (loss) income as adjusted for purposes of computing diluted earnings per common share $(5,269) (1,733) 1,389
table: Shares (Denominator):
table: Weighted average number of shares:
table: Outstanding during period 1,088,730 1,078,409 635,576
table: Non-vested restricted stock (17,289) (12,543) (7,768)
table: Weighted average shares outstanding for computing basic earnings per common share 1,071,441 1,065,866 627,808
table: Incremental common shares attributable to dilutive securities:
table: Shares issuable under convertible securities — — 10
table: Shares issuable under incentive compensation plans — — 875
table: Number of shares as adjusted for purposes of computing diluted (loss) earnings per common share 1,071,441 1,065,866 628,693
table: Basic (loss) earnings per common share $(4.92) (1.63) 2.21
table: Diluted (loss) earnings per common share(1) $(4.92) (1.63) 2.21
question: Analyse this data from a financial earnings document. What is the average annual amount of unvested restricted stock awards that are antidilutive excluded in 2017, 2018 and 2019?