On 17 September, the chief executive of the derivatives association, Robert Pickel, told the House Agriculture Committee in America: "Not all standardised contracts can be cleared," because even if they have standardised economic terms, many derivatives contracts will be "difficult if not impossible to clear" since the counterparty depends on liquidity, trading volume and daily pricing. This would, Pickel said, make "it difficult for a clearing house to calculate collateral requirements consistent with prudent risk management."