five-year performance comparison 2013 the following graph provides an indicator of cumulative total shareholder returns for the corporation as compared to the peer group index ( described above ) , the dj trans , and the s&p 500 . the graph assumes that $ 100 was invested in the common stock of union pacific corporation and each index on december 31 , 2012 and that all dividends were reinvested . the information below is historical in nature and is not necessarily indicative of future performance . purchases of equity securities 2013 during 2017 , we repurchased 37122405 shares of our common stock at an average price of $ 110.50 . the following table presents common stock repurchases during each month for the fourth quarter of 2017 : period total number of shares purchased [a] average price paid per share total number of shares purchased as part of a publicly announced plan or program [b] maximum number of shares remaining under the plan or program [b] .
[a] total number of shares purchased during the quarter includes approximately 323670 shares delivered or attested to upc by employees to pay stock option exercise prices , satisfy excess tax withholding obligations for stock option exercises or vesting of retention units , and pay withholding obligations for vesting of retention shares . [b] effective january 1 , 2017 , our board of directors authorized the repurchase of up to 120 million shares of our common stock by december 31 , 2020 . these repurchases may be made on the open market or through other transactions . our management has sole discretion with respect to determining the timing and amount of these transactions. .
Period Total Number of Shares Purchased [a] Average Price Paid Per Share Total Number of Shares Purchased as Part of a Publicly AnnouncedPlan or Program [b] Maximum Number of Shares Remaining Under the Plan or Program [b]
Oct. 1 through Oct. 31 3,831,636 $113.61 3,800,000 89,078,662
Nov. 1 through Nov. 30 3,005,225 117.07 2,937,410 86,141,252
Dec. 1 through Dec. 31 2,718,319 130.76 2,494,100 83,647,152
Total 9,555,180 $119.58 9,231,510 N/A
period total number of shares purchased [a] average price paid per share total number of shares purchased as part of a publicly announcedplan or program [b] maximum number of shares remaining under the plan or program [b]
oct . 1 through oct . 31 3831636 $ 113.61 3800000 89078662
nov . 1 through nov . 30 3005225 117.07 2937410 86141252
dec . 1 through dec . 31 2718319 130.76 2494100 83647152
total 9555180 $ 119.58 9231510 n/a