<ARTICLE>  5
<LEGEND>   This schedule contains summary financial information extracted
           from the Balance Sheet and Statement of Operations included in
           the Company's Form 10-K for the year ended March 31, 1998 and
           is qualified in its entirety by reference to such Financial
           Statements.
</LEGEND> 
<MULTIPLIER> 1,000 
       
                                                  
<FISCAL-YEAR-END>                          Mar-31-1998  Mar-31-1997
<PERIOD-START>                             Apr-01-1997  Apr-01-1996
<PERIOD-END>                               Mar-31-1998  Mar-31-1997
<PERIOD-TYPE>                              12-MOS       12-MOS
<CASH>                                        24,985       44,225
<SECURITIES>                                       0       10,833
<RECEIVABLES>                                 71,343       36,826
<ALLOWANCES>                                   1,327        1,055
<INVENTORY>                                   18,400       11,837
<CURRENT-ASSETS>                             126,923      109,695
<PP&E>                                       382,875      231,888
<DEPRECIATION>                                92,392       53,013
<TOTAL-ASSETS>                               478,223      373,389
<CURRENT-LIABILITIES>                         38,224       37,868
<BONDS>                                      230,000      230,000
<PREFERRED-MANDATORY>                              0            0
<PREFERRED>                                        0            0
<COMMON>                                          43           41
<OTHER-SE>                                   182,409       95,401
<TOTAL-LIABILITY-AND-EQUITY>                 478,223      373,389
<SALES>                                      356,194      263,209
<TOTAL-REVENUES>                             356,194      263,209
<CGS>                                        225,599      156,277
<TOTAL-COSTS>                                225,599      156,277
<OTHER-EXPENSES>                              22,504       17,615
<LOSS-PROVISION>                                   0            0
<INTEREST-EXPENSE>                             8,194        3,329
<INCOME-PRETAX>                               99,897       85,988
<INCOME-TAX>                                  29,969       25,400
<INCOME-CONTINUING>                           69,928       60,588
<DISCONTINUED>                                     0            0
<EXTRAORDINARY>                                    0            0
<CHANGES>                                          0            0
<NET-INCOME>                                  69,928       61,745
<EPS-PRIMARY>                                  $1.66        $1.52
<EPS-DILUTED>                                  $1.40        $1.35