The answer is that the trust fund is populated with special non-marketable securities whose value is not subject to the vicissitudes of the market.

FORBES: A Modest Proposal to Avoid Debt Limit Disaster

The audited financial statements of venture funds (if any exist) typically state that the majority of the portfolio consists of non-marketable securities the valuations of which are determined by the manager of the fund.

FORBES: The Art of Theft: How Corporate Fiduciaries Steal From American��s Pensions (February 2, 2005 )