I think you are assuming the derivatives in question are wild, complex, speculative derivatives. This is almost certainly not the case. They are most likely lon

I think you are assuming the derivatives in question are wild, complex, speculative derivatives. This is almost certainly not the case. They are most likely long dated interest swaps. Pension funds have a duration problem, they are managing long term liabilities (what they owe to pensioners) and need to ensure they have enough assets to cover the present value of those liabilities. If interest rates move, then the present value of those liabilities may change a lot because of the new discounting. So they try to reduce that risk, either by buying assets that behave in a similar way with respect to interest rates, or by entering into long dated interest rate swaps. I think the leveraged repo positions they are refering to is doing the same thing as an interest rate swap by going long a long term gilt and short a short term gilt (or the other way round), but basically they try to create an interest rate mismatch to take some duration exposure. So this is pension funds reducing the risks, not speculating. The systemic risk here seems to be mostly a concentration problem and feedback loop. I.e. the more interest rates move up the more pension funds need to sell gilts to hedge their duration or post collateral, the more gilt prices collapse, the more interest rates move up.