purchases of equity securities 2013 during 2018 , we repurchased 57669746 shares of our common stock at an average price of $ 143.70 . the following table presents common stock repurchases during each month for the fourth quarter of 2018 : 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 17391 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 6,091,605 $158.20 6,087,727 32,831,024
Nov. 1 through Nov. 30 3,408,467 147.91 3,402,190 29,428,834
Dec. 1 through Dec. 31 3,007,951 148.40 3,000,715 26,428,119
Total 12,508,023 $153.04 12,490,632 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 6091605 $ 158.20 6087727 32831024
nov . 1 through nov . 30 3408467 147.91 3402190 29428834
dec . 1 through dec . 31 3007951 148.40 3000715 26428119
total 12508023 $ 153.04 12490632 n/a