The Company utilized the “simplified method” to determine the expected stock option life due to insufficient historical experience to estimate the exercise patterns of the stock options granted.
The Company began granting stock options at the time of its initial public offering in April 2008.
Expected volatility is based on a weighted average of historic volatilities of traded common stock of peer companies (regulated water companies) over the expected term of the stock options and historic volatilities of the Company’s common stock during the period it has been publicly traded.
The dividend yield is based on the Company’s expected dividend payments and the stock price on the date of grant.
The risk-free interest rate is the market yield on U. S.  Treasury strips with maturities similar to the expected term of the stock options.
The exercise price of the stock options is equal to the fair market value of the underlying stock on the date of option grant.
Stock options granted vest over periods ranging from one to three years and expire seven years from the effective date of the grant.
The fair value of each option is estimated on the date of grant using the Black-Scholes option-pricing model.
The value of stock options at the date of the grant is amortized through expense over the requisite service period using the straight-line method.
As of December 31, 2012, $3,534 of total unrecognized compensation costs related to the nonvested stock options is expected to be recognized over the remaining weighted-average period of 1.6 years.
The total grant date fair value of stock options vested during the years ended December 31, 2012, 2011 and 2010 was $3,219, $4,578 and $4,505, respectively.
The table below summarizes stock option activity for the year ended December 31, 2012:
## Table 0 ##
The following table summarizes additional information regarding stock options exercised during the years ended December 31, 2012, 2011 and 2010:
## Table 1 ##
Restricted Stock Units In 2012, 2011 and 2010, the Company granted restricted stock units to certain employees under the Plan.
The restricted stock units vest ratably over the three-year performance period beginning January 1 of the year of grant (the “Performance Period”); however, distribution of the shares is contingent upon the achievement of internal performance measures and, separately, certain market thresholds over the Performance Period.
During 2012, 2011 and 2010, the Company granted restricted stock units to non-employee directors under the Plan.
The restricted stock units vested on the date of grant; however, distribution of the shares will be made within 30 days of the earlier of (a) 15 months after grant date or (b) the participant’s separation from service.
Because these restricted stock units vested on grant date, the total grant date fair value was recorded in operation and maintenance expense included in the expense table above on the grant date.
Dunbar, West Virginia Water Main Break Class Action Litigation On the evening of June 23, 2015, a 36-inch pre-stressed concrete transmission water main, installed in the early 1970s, failed.
The water main is part of WVAWC’s West Relay pumping station located in the City of Dunbar.
The failure of the main caused water outages and low pressure to up to approximately 25,000 WVAWC customers.
In the early morning hours of June 25, 2015, crews completed a repair, but that same day, the repair developed a leak.
On June 26, 2015, a second repair was completed and service was restored that day to approximately 80% of the impacted customers, and to the remaining approximately 20% by the next morning.
The second repair showed signs of leaking but the water main was usable until June 29, 2015 to allow tanks to refill.
The system was reconfigured to maintain service to all but approximately 3,000 customers while a final repair was completed safely on June 30, 2015.
Water service was fully restored on July 1, 2015 to all customers affected by this event.
On June 2, 2017, a class action complaint was filed in West Virginia Circuit Court in Kanawha County against WVAWC on behalf of a purported class of residents and business owners who lost water service or pressure as a result of the Dunbar main break.
The complaint alleges breach of contract by WVAWC for failure to supply water, violation of West Virginia law regarding the sufficiency of WVAWC’s facilities and negligence by WVAWC in the design, maintenance and operation of the water system.
The plaintiffs seek unspecified alleged damages on behalf of the class for lost profits, annoyance and inconvenience, and loss of use, as well as punitive damages for willful, reckless and wanton behavior in not addressing the risk of pipe failure and a large outage.
On October 12, 2017, WVAWC filed with the court a motion seeking to dismiss all of the plaintiffs’ counts alleging statutory and common law tort claims.
Furthermore, WVAWC asserts that the PSC, and not the court, has primary jurisdiction over allegations involving violations of the applicable tariff, the public utility code and related rules.
This motion remains pending.
The Company and WVAWC believe that WVAWC has valid, meritorious defenses to the claims raised in this class action complaint.
WVAWC is vigorously defending itself against these allegations.
Given the current stage of this proceeding, the Company cannot reasonably estimate the amount of any reasonably possible losses or a range of such losses related to this proceeding.
Note 16: Earnings per Common Share The following is a reconciliation of the numerator and denominator for basic and diluted earnings per share (“EPS”) calculations for the years ended December 31:
## Table 2 ##
The effect of dilutive common stock equivalents is related to RSUs and performance stock units granted under the 2007 and 2017 Omnibus Equity Compensation Plans, as well as shares purchased under the ESPP.
Less than one million share-based awards were excluded from the computation of diluted EPS for the years ended December 31, 2017, 2016 and 2015 because their effect would have been anti-dilutive under the treasury stock method.
ÿþOperating Revenues  The following tables and the ensuing discussions provide explanations for the variances related to the three  components of operating revenues  water services revenues, wastewater services revenues and other revenues:  @T@  For the Years Ended December 31,  @T@  Note: The correlation between water revenues and billed water volumes shown in the preceding tables is impacted by the California drought.
  In 2015, and to a lesser extent in 2016, California experienced a severe drought.
 In April 2015, the Governor mandated water usage  restrictions to reduce overall water usage by 25% in the state compared to 2013 levels.
 In April 2017, the mandated water usage  restrictions were removed.
 In California, revenue is decoupled from sales volume through the WRAM/MCBA, aligning our water  conservation goals with those of the state and our customers, and therefore usage reductions do not impact earnings.
  In 2017, operating revenues increased $87 million, or 3.
0%, primarily due to a:  "  $81 million increase from authorized rate increases, including infrastructure surcharges, principally to  fund investment growth in various states;  "  $43 million increase attributable to water and wastewater acquisitions, as well as organic growth in  existing systems; and a  "  $9 million increase resulting from higher wastewater treatment volumes and an increase in private fire  service connections; partially offset by a  "  $48 million decrease due to lower water services demand, including a $15 million reduction due to  warmer weather in 2016.
  In 2016, operating revenues increased $128 million, or 4.
7%, primarily due to a:  "  $92 million increase from authorized rate increases, including infrastructure surcharges, principally to  fund investment growth in various states;
## Table 3 ##
## Table 4 ##
The Company’s 2017 reported tax rate includes $160.9 million of net tax benefits associated with the Tax Act, $6.2 million of net tax benefits on special gains and charges, and net tax benefits of $25.3 million associated with discrete tax items.
In connection with the Company’s initial analysis of the impact of the Tax Act, as noted above, a provisional net discrete tax benefit of $160.9 million was recorded in the period ended December 31, 2017, which includes $321.0 million tax benefit for recording deferred tax assets and liabilities at the U. S.  enacted tax rate, and a net expense for the one-time transition tax of $160.1 million.
While the Company was able to make an estimate of the impact of the reduction in the U. S.  rate on deferred tax assets and liabilities and the one-time transition tax, it may be affected by other analyses related to the Tax Act, as indicated above.
Special (gains) and charges represent the tax impact of special (gains) and charges, as well as additional tax benefits utilized in anticipation of U. S.  tax reform of $7.8 million.
During 2017, the Company recorded a discrete tax benefit of $39.7 million related to excess tax benefits, resulting from the adoption of accounting changes regarding the treatment of tax benefits on share-based compensation.
The extent of excess tax benefits is subject to variation in stock price and stock option exercises.
In addition, the Company recorded net discrete expenses of $14.4 million related to recognizing adjustments from filing the 2016 U. S.  federal income tax return and international adjustments due to changes in estimates, partially offset by the release of reserves for uncertain tax positions due to the expiration of statute of limitations in state tax matters.
During 2016, the Company recognized net expense related to discrete tax items of $3.9 million.
The net expenses were driven primarily by recognizing adjustments from filing the Company’s 2015 U. S.  federal income tax return, partially offset by settlement of international tax matters and remeasurement of certain deferred tax assets and liabilities resulting from the application of updated tax rates in international jurisdictions.
Net expense was also impacted by adjustments to deferred tax asset and liability positions and the release of reserves for uncertain tax positions due to the expiration of statute of limitations in non-U.
S.  jurisdictions.
During 2015, the Company recognized net benefits related to discrete tax items of $63.3 million.
The net benefits were driven primarily by the release of $20.6 million of valuation allowances, based on the realizability of foreign deferred tax assets and the ability to recognize a worthless stock deduction of $39.0 million for the tax basis in a wholly-owned domestic subsidiary.
A reconciliation of the beginning and ending amount of gross liability for unrecognized tax benefits is as follows:
## Table 5 ##
The total amount of unrecognized tax benefits, if recognized would have affected the effective tax rate by $47.1 million as of December 31, 2017, $57.5 million as of December 31, 2016 and $59.2 million as of December 31, 2015.
The Company recognizes interest and penalties related to unrecognized tax benefits in its provision for income taxes.
During 2017, 2016 and 2015 the Company released $0.9 million, $2.9 million and $1.4 million related to interest and penalties, respectively.
The Company had $9.3 million, $10.2 million and $13.1 million of accrued interest, including minor amounts for penalties, at December 31, 2017, 2016, and 2015, respectively

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td>Shares</td><td> Weighted Average Exercise Price (per share)</td><td> Weighted Average Remaining Life (years)</td><td> Aggregate Intrinsic Value</td></tr><tr><td>Options outstanding at January 1, 2012</td><td>3,112</td><td>$22.70</td><td></td><td></td></tr><tr><td>Granted</td><td>649</td><td>34.14</td><td></td><td></td></tr><tr><td>Forfeited or expired</td><td>-101</td><td>27.76</td><td></td><td></td></tr><tr><td>Exercised</td><td>-1,025</td><td>21.57</td><td></td><td></td></tr><tr><td>Options outstanding at December 31, 2012</td><td>2,635</td><td>$25.77</td><td>4.2</td><td>$29,946</td></tr><tr><td>Exercisable at December 31, 2012</td><td>1,378</td><td>$22.17</td><td>3.2</td><td>$20,610</td></tr></table>
<table><tr><td></td><td> 2012</td><td> 2011</td><td>2010</td></tr><tr><td>Intrinsic value</td><td>$14,515</td><td>$3,026</td><td>$333</td></tr><tr><td>Exercise proceeds</td><td>22,112</td><td>8,991</td><td>3,010</td></tr><tr><td>Income tax benefit (shortfall)</td><td>4,017</td><td>511</td><td>-89</td></tr></table>
<table><tr><td></td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>Numerator:</td><td></td><td></td><td></td></tr><tr><td>Net income attributable to common stockholders</td><td>$426</td><td>$468</td><td>$476</td></tr><tr><td>Denominator:</td><td></td><td></td><td></td></tr><tr><td>Weighted average common shares outstanding—Basic</td><td>178</td><td>178</td><td>179</td></tr><tr><td>Effect of dilutive common stock equivalents</td><td>1</td><td>1</td><td>1</td></tr><tr><td>Weighted average common shares outstanding—Diluted</td><td>179</td><td>179</td><td>180</td></tr></table>
<table><tr><td></td><td colspan="3">For the Years Ended December 31,</td><td colspan="2" rowspan="2"Increase(Decrease) 2017 vs. 2016></td><td colspan="2" rowspan="2"Increase(Decrease) 2016 vs. 2015></td></tr><tr><td></td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>(Dollars in millions)</td><td></td><td></td><td></td><td>$</td><td>%</td><td>$</td><td>%</td></tr><tr><td>Billed water services revenues:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Residential</td><td>$1,654</td><td>$1,592</td><td>$1,536</td><td>$62</td><td>3.9</td><td>$56</td><td>3.6</td></tr><tr><td>Commercial</td><td>603</td><td>580</td><td>559</td><td>23</td><td>4.0</td><td>21</td><td>3.8</td></tr><tr><td>Industrial</td><td>137</td><td>134</td><td>130</td><td>3</td><td>2.2</td><td>4</td><td>3.1</td></tr><tr><td>Public and other</td><td>351</td><td>338</td><td>331</td><td>13</td><td>3.8</td><td>7</td><td>2.1</td></tr><tr><td>Other</td><td>31</td><td>53</td><td>39</td><td>-22</td><td>-41.5</td><td>14</td><td>35.9</td></tr><tr><td>Total billed water services revenues</td><td>2,776</td><td>2,697</td><td>2,595</td><td>79</td><td>2.9</td><td>102</td><td>3.9</td></tr><tr><td>Unbilled water services revenues</td><td>-11</td><td>13</td><td>-3</td><td>-24</td><td>-184.6</td><td>16</td><td>-533.3</td></tr><tr><td>Total water services revenues</td><td>2,765</td><td>2,710</td><td>2,592</td><td>55</td><td>2.0</td><td>118</td><td>4.6</td></tr><tr><td>Wastewater services revenues</td><td>142</td><td>112</td><td>97</td><td>30</td><td>26.8</td><td>15</td><td>15.5</td></tr><tr><td>Other revenues</td><td>51</td><td>49</td><td>54</td><td>2</td><td>4.1</td><td>-5</td><td>-9.3</td></tr><tr><td>Total operating revenues</td><td>$2,958</td><td>$2,871</td><td>$2,743</td><td>$87</td><td>3.0</td><td>$128</td><td>4.7</td></tr></table>
<table><tr><td></td><td colspan="3">For the Years Ended December 31,</td><td colspan="2" rowspan="2"Increase(Decrease) 2017 vs. 2016></td><td colspan="2" rowspan="2"Increase(Decrease) 2016 vs. 2015></td></tr><tr><td></td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>(Gallons in millions)</td><td></td><td></td><td></td><td>Gallons%</td><td></td><td>Gallons%</td><td></td></tr><tr><td>Billed water services volumes:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Residential</td><td>174,420</td><td>174,599</td><td>175,653</td><td>-179</td><td>-0.1</td><td>-1,054</td><td>-0.6</td></tr><tr><td>Commercial</td><td>82,147</td><td>82,489</td><td>81,772</td><td>-342</td><td>-0.4</td><td>717</td><td>0.9</td></tr><tr><td>Industrial</td><td>39,404</td><td>38,465</td><td>38,991</td><td>939</td><td>2.4</td><td>-526</td><td>-1.3</td></tr><tr><td>Public and other</td><td>51,341</td><td>50,678</td><td>51,324</td><td>663</td><td>1.3</td><td>-646</td><td>-1.3</td></tr><tr><td>Total billed water services volumes</td><td>347,312</td><td>346,231</td><td>347,740</td><td>1,081</td><td>0.3</td><td>-1,509</td><td>-0.4</td></tr></table>
<table><tr><td>(millions)</td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>Balance at beginning of year</td><td>$75.9</td><td>$74.6</td><td>$78.7</td></tr><tr><td>Additions based on tax positions related to the current year</td><td>3.2</td><td>8.8</td><td>5.8</td></tr><tr><td>Additions for tax positions of prior years</td><td>-</td><td>2.1</td><td>0.9</td></tr><tr><td>Reductions for tax positions of prior years</td><td>-4.9</td><td>-1.0</td><td>-8.8</td></tr><tr><td>Reductions for tax positions due to statute of limitations</td><td>-14.0</td><td>-5.5</td><td>-1.6</td></tr><tr><td>Settlements</td><td>-10.8</td><td>-2.0</td><td>-4.2</td></tr><tr><td>Assumed in connection with acquisitions</td><td>10.0</td><td>-</td><td>8.0</td></tr><tr><td>Foreign currency translation</td><td>2.1</td><td>-1.1</td><td>-4.2</td></tr><tr><td>Balance at end of year</td><td>$61.5</td><td>$75.9</td><td>$74.6</td></tr></table>

Question: what is the percentage change in the balance of gross liability for unrecognized tax benefits from 2016 to 2017?
Answer: -0.18972
Reasoning program: subtract(61.5,75.9), divide(#0,75.9)