<TABLE> <S> <C>

<PAGE>

<ARTICLE> 5
<RESTATED>
<MULTIPLIER> 1,000

<S>                             <C>                     <C>                     <C>                     <C>
<PERIOD-TYPE>                   12-MOS                   9-MOS                   6-MOS                   3-MOS
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1998             DEC-31-1998             DEC-31-1998
<PERIOD-END>                               DEC-31-1998             SEP-30-1998             JUN-30-1998             MAR-31-1998
<CASH>                                           4,300                  17,500                   4,600                   8,400
<SECURITIES>                                         0                       0                       0                       0
<RECEIVABLES>                                  240,900                 214,900                 192,100                 171,300
<ALLOWANCES>                                         0                       0                       0                       0
<INVENTORY>                                     10,200                  10,600                  10,500                  11,200
<CURRENT-ASSETS>                               292,900                 262,100                 238,200                 225,900
<PP&E>                                       6,175,900               5,628,100               5,477,600               5,327,200
<DEPRECIATION>                               3,955,100               3,828,900               3,747,400               3,670,300
<TOTAL-ASSETS>                               2,574,000               2,119,600               2,023,200               1,930,800
<CURRENT-LIABILITIES>                          250,500                 235,100                 285,600                 283,800
<BONDS>                                      1,288,600                 867,200                 770,900                 715,700
<PREFERRED-MANDATORY>                                0                       0                       0                       0
<PREFERRED>                                          0                       0                       0                       0
<COMMON>                                         1,000                   1,000                   1,000                   1,000
<OTHER-SE>                                     614,200                 602,500                 571,900                 545,400
<TOTAL-LIABILITY-AND-EQUITY>                 2,574,000               2,119,600               2,023,200               1,930,800
<SALES>                                      1,602,400               1,194,800                 819,600                 407,900
<TOTAL-REVENUES>                             1,672,700               1,257,200                 871,300                 450,100
<CGS>                                          565,600                 376,500                 243,000                 118,000
<TOTAL-COSTS>                                  776,200                 544,200                 375,400                 186,200
<OTHER-EXPENSES>                               715,400                 551,600                 383,000                 190,500
<LOSS-PROVISION>                                     0                       0                       0                       0
<INTEREST-EXPENSE>                              60,300                  40,700                  26,300                  12,600
<INCOME-PRETAX>                                 51,200                  65,700                  44,200                  32,600
<INCOME-TAX>                                  (85,200)                (52,700)                (36,600)                (15,400)
<INCOME-CONTINUING>                            136,400                 118,400                  80,800                  48,000
<DISCONTINUED>                                       0                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0                       0
<CHANGES>                                            0                       0                       0                       0
<NET-INCOME>                                   136,400                 118,400                  80,800                  48,000
<EPS-BASIC>                                       1.40                    1.22                    0.83                    0.49
<EPS-DILUTED>                                     1.39                    1.21                    0.83                    0.49



</TABLE>