text: A summary of the changes in common shares available for awards under the Omnibus Incentive Plan and Predecessor Plans
follows:
text: (1) As of December 31, 2018, there were 1,478 restricted stock shares issued for new awards under the Omnibus Incentive Plan and (5,024) restricted stock shares forfeited that were not yet reflected by our Recordkeeper. The table above (shares available under the Omnibus Incentive Plan) reflects this activity as occurred, creating a reconciling difference between shares issued and number of shares available under the Omnibus Plan.
text: (2) Director units granted and deferred include the impact of share-settled dividends earned and deferred on deferred shares.
text: (3) The Omnibus Incentive Plan and 2005 Contingent Stock Plan permit withholding of taxes and other charges that may be required by law to be paid attributable to awards by withholding a portion of the shares attributable to such awards.
text: (4) The above table excludes approximately1.2 million contingently issuable shares under the PSU awards and SLO awards, which represents the maximum number of shares that could be issued under those plans as of December 31, 2019.
text: We record share-based incentive compensation expense in selling, general and administrative expenses and cost of sales on our Consolidated Statements of Operations for both equity-classified awards and liability-classified awards. We record a corresponding credit to additional paid-in capital within stockholders’ deficit for equity-classified awards, and to either a current or non-current liability for liability-classified awards based on the fair value of the share-based incentive compensation awards at the date of grant. Total expense for the liability-classified awards continues to be remeasured to fair value at the end of each reporting period. We recognize an expense or credit reflecting the straight-line recognition, net of estimated forfeitures, of the expected cost of the program. The number of PSUs earned may equal, exceed or be less than the targeted number of shares depending on whether the performance criteria are met, surpassed or not met.

Table:
2019
2018
2017
Number of shares available, beginning of year
4,489,347
3,668,954
5,385,870
Newly Registered Shares under Omnibus Incentive Plan
—
2,199,114
—
Restricted stock shares issued for new awards(1)
—
(571,438 )
(480,283)
Restricted stock shares forfeited(1)
105,960
91,542
184,235
Restricted stock units awarded
(819,808)
(219,923 )
(351,946)
Restricted stock units forfeited
96,534
64,122
288,801
Shares issued for 2014 Special PSU Awards
—
(658,783 )
(749,653)
Shares issued for 2015 Three-Year PSU Awards
—
(129,139 )
—
Shares issued for 2014 Three-Year PSU Awards
—
—
(636,723)
Restricted stock units awarded for SLO Awards
(46,195)
(23,478 )
(44,254)
SLO units forfeited
1,580
817
3,639
Director shares granted and issued
(22,015)
(10,560 )
(15,491)
Director units granted and deferred(2)
(6,262)
(16,505 )
(17,008)
Shares withheld for taxes(3)
249,368
94,624
101,767
Number of shares available, end of year(4)
4,048,509
4,489,347
3,668,954

Questions:
question: What is the percentage difference of shares withheld for taxes for 2018 to 2019?
answer: 163.54
derivation: (249,368-94,624)/94,624
scale: percent
question: What is the Number of shares available, end of year expressed as a percentage of Number of shares available, beginning of year for 2019? 
answer: 90.18
derivation: 4,048,509/4,489,347
scale: percent
question: What is the average annual Number of shares available, end of year for 2017-2019?
answer: 4068936.67
derivation: (4,048,509+4,489,347+3,668,954)/3