Year Ended December 31,
Year Ended December 31,
Year Ended December 31,
2019
2018
2017
Distributed earnings
$43,207
$39,627
$32,709
Undistributed earnings
70,683
42,470
81,432
Net income
$113,890
$82,097
$114,141
Class A common stock:
Basic net income available to common stockholders
$76,294
$54,715
$75,413
Basic weighted average common shares outstanding
26,763
26,354
25,685
Basic earnings per share
$2.85
$2.08
$2.94
Diluted net income available to common stockholders
$76,555
$54,937
$75,698
Effect of potential exercise of stock options
279
324
288
Diluted weighted average common shares outstanding
27,042
26,678
25,973
Diluted earnings per share
$2.83
$2.06
$2.91
Class B common stock:
Basic net income available to common stockholders
$37,596
$27,382
$38,728
Basic weighted average common shares outstanding
13,188
13,189
13,190
Basic earnings per share
$2.85
$2.08
$2.94
Diluted net income available to common stockholders
$37,335
$27,160
$38,443
Diluted weighted average common shares outstanding
13,188
13,189
13,190
Diluted earnings per share
$2.83
$2.06
$2.91
For the years ended December 31, 2019, 2018 and 2017, options to purchase 288,133 shares, 293,898 shares and 265,866
6 .
earnings per share .
under asc 260 earnings per share the two-class method is an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared -or accumulated and participation rights in undistributed earnings .
under that method basic and diluted earnings per share data are presented for each class of common stock .
in applying the two-class method we determined that undistributed earnings should be allocated equally on a per share basis between class a and class b common stock .
under our certificate of incorporation the holders of the common stock are entitled to participate ratably on a share-for-share basis as if all shares of common stock were of a single class in such dividends as may be declared by the board of directors .
during the years ended december 31 2019 2018 and 2017 we declared and paid quarterly dividends in the amount of $ 0 .
27 $ 0 .
25 and $ 0 .
21 per share on both classes of common stock .
basic earnings per share has been computed by dividing net income available to common stockholders by the weighted average number of shares of common stock outstanding during each period .
shares issued during the period and shares reacquired during the period are weighted for the portion of the period in which the shares were outstanding .
diluted earnings per share have been computed in a manner consistent with that of basic earnings per share while giving effect to all potentially dilutive common shares that were outstanding during each period .
the net income available to common stockholders and weighted average number of common shares outstanding used to compute basic and diluted earnings per share for each class of common stock are as follows -in thousands except per share amounts : .
for the years ended december 31 2019 2018 and 2017 options to purchase 288133 shares 293898 shares and 265866 shares respectively were outstanding but not included in the computation of diluted earnings per share because the options ' effect would have been anti-dilutive .
for the years ended december 31 2019 2018 and 2017 there were 338748 shares 420524 shares and 463800 shares respectively issued from the exercise of stock options .

Question: What does the two-class method mean under ASC 360?
Answer: an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared (or accumulated) and participation rights in undistributed earnings