60. In April 1997 and subsequently until 2002, the Principal Employer used the monies in the Scheme's fund to fund its own contributions to the Scheme, including its contributions for those employees in both the C Plan and the M Plan and the cost of LPI increases. A surplus had begun to accumulate in 1992. There was a sharp rise in the surplus in the year ending December 1997 which continued until 2000. The major cause of the increase was good investment performance which more than offset the change to valuation assumptions to take account of the increased longevity of members. Three of the complainants say that a major cause of the increase was the continuing effect of IBM's actions in making more of its salary benefits non-pensionable.