<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<RESTATED>

<S>                             <C>                     <C>                     <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   6-MOS                   9-MOS                   12-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1997             DEC-31-1996
<PERIOD-START>                             JAN-01-1997             JAN-01-1997             JAN-01-1997             JAN-01-1996
<PERIOD-END>                               MAR-31-1997             JUN-30-1997             SEP-30-1997             DEC-31-1996
<CASH>                                       1,101,747                 985,864                 706,138                 708,817
<SECURITIES>                                         0                       0                       0                       0
<RECEIVABLES>                                2,956,250               3,765,533               3,375,097               2,823,570
<ALLOWANCES>                                 (304,181)               (330,836)               (343,457)               (285,385)
<INVENTORY>                                     46,385                  46,385                  42,062                  46,385
<CURRENT-ASSETS>                             5,906,257               7,472,834               6,921,231               5,004,365
<PP&E>                                      60,552,512              61,168,316              62,328,116              60,079,551
<DEPRECIATION>                              21,504,376              21,910,752              22,321,061              21,079,569
<TOTAL-ASSETS>                              47,852,562              49,620,778              49,820,824              46,874,799
<CURRENT-LIABILITIES>                        6,863,721               9,571,167               8,657,885               5,137,365
<BONDS>                                      5,212,000               5,825,503               6,239,455               5,212,000
<PREFERRED-MANDATORY>                                0                       0                       0                       0
<PREFERRED>                                          0                       0                       0                       0
<COMMON>                                     1,506,512               1,506,512               1,506,512               1,506,512
<OTHER-SE>                                  14,076,531              14,277,417              14,759,533              14,119,933
<TOTAL-LIABILITY-AND-EQUITY>                47,852,562              49,620,778              49,820,824              46,874,799
<SALES>                                      4,844,457              11,226,426              18,830,951              23,331,018
<TOTAL-REVENUES>                             5,168,027              12,168,935              20,339,562              24,704,786
<CGS>                                        2,226,882               5,584,585              10,699,579              11,915,671
<TOTAL-COSTS>                                4,172,624               9,618,623              15,920,946              19,437,920
<OTHER-EXPENSES>                                     0                       0                       0                       0
<LOSS-PROVISION>                                46,480                  67,442                 100,420                 153,960
<INTEREST-EXPENSE>                             185,137                 399,523                 593,685                 659,264
<INCOME-PRETAX>                                472,734               1,353,778               2,704,418               3,295,267
<INCOME-TAX>                                   189,770                 543,500               1,085,605               1,313,969
<INCOME-CONTINUING>                            282,964                 810,278               1,618,813               1,981,298
<DISCONTINUED>                                       0                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0                       0
<CHANGES>                                            0                       0                       0                       0
<NET-INCOME>                                   282,964                 810,278               1,618,813               1,981,298
<EPS-PRIMARY>                                      .19                     .54                    1.07                    1.31
<EPS-DILUTED>                                      .19                     .54                    1.07                    1.31


</TABLE>