<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5

<S>                                        <C>                     <C>                     <C>                     <C>
<PERIOD-TYPE>                              YEAR                    3-MOS                   3-MOS                   3-MOS
<FISCAL-YEAR-END>                          DEC-31-1996             DEC-31-1997             DEC-31-1997             DEC-31-1997
<PERIOD-END>                               DEC-31-1996             MAR-31-1997             JUN-30-1997             SEP-30-1997
<CASH>                                          26,087                  24,661                  40,135                  45,301
<SECURITIES>                                    12,727                  13,653                  14,470                  15,251
<RECEIVABLES>                                   61,856                  78,731                  88,424                  93,534
<ALLOWANCES>                                     1,670                   2,629                   2,986                   3,295
<INVENTORY>                                          0                       0                       0                       0
<CURRENT-ASSETS>                               121,079                 138,050                 163,082                 182,215
<PP&E>                                          33,865                  36,655                  43,031                  48,878
<DEPRECIATION>                                  13,274                  14,220                  15,733                  17,781
<TOTAL-ASSETS>                                 147,644                 166,282                 197,640                 220,315
<CURRENT-LIABILITIES>                           48,826                  56,149                  73,537                  76,052
<BONDS>                                              0                       0                       0                       0
<PREFERRED-MANDATORY>                                0                       0                       0                       0
<PREFERRED>                                          0                       0                       0                       0
<COMMON>                                           517                     523                     529                     535
<OTHER-SE>                                           0                       0                       0                       0
<TOTAL-LIABILITY-AND-EQUITY>                   147,644                 166,282                 197,640                 220,315
<SALES>                                              0                       0                       0                       0
<TOTAL-REVENUES>                               272,878                  82,222                 178,748                 287,343
<CGS>                                                0                       0                       0                       0
<TOTAL-COSTS>                                  233,422                  69,176                 151,102                 243,686
<OTHER-EXPENSES>                                 (868)                   (311)                 (1,006)                 (1,573)
<LOSS-PROVISION>                                   518                     434                     776                   1,118
<INTEREST-EXPENSE>                                  71                      33                      76                     107
<INCOME-PRETAX>                                 40,253                  13,324                  28,576                  45,122
<INCOME-TAX>                                    16,228                   5,370                  11,501                  18,134
<INCOME-CONTINUING>                             24,025                   7,954                  17,075                  26,988
<DISCONTINUED>                                       0                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0                       0
<CHANGES>                                            0                       0                       0                       0
<NET-INCOME>                                    24,025                   7,954                  17,075                  26,988
<EPS-PRIMARY>                                     0.48                    0.15                    0.32                    0.51
<EPS-DILUTED>                                     0.42                    0.14                    0.30                    0.47



</TABLE>