Collateral and Monetary Policy: A Puzzle

A stylized fact about post-crisis economies is that asset markets have become segmented with “safe assets” trading differently from assets more generally. I have argued elsewhere that the collateralization of financial sector liabilities has played an important role in this segmentation of markets.

I believe that this creates a puzzle for the implementation of monetary policy that provides at least a partial explanation for why we are stuck at the zero lower bound. Consider the consequences of an increase in the policy rate by 25 bps. This has the effect of lowering the price of ultra-short-term Treasury debt, and particularly when combined with a general policy of raising the policy rate over a period of months or years this policy should have the effect of lowering the price of longer term Treasuries as well (due to the fact that long-term yields can be arbitraged by rolling over short-term debt).

A decline in the price of long-term Treasuries will have the effect of reducing the dollar value of the stock of outstanding Treasuries (as long as the Treasury does not have a policy of responding to the price effects of monetary policy by issuing more Treasuries). But now consider what happens in the –segmented — market for Treasury debt. Assuming that demand for Treasuries is downward sloping, then the fact that contractionary monetary policy tends to shrink the stock of Treasuries itself puts upward pressure on the price of Treasuries that, particularly when demand for Treasuries is inelastic, will tend to offset and may even entirely counteract the tendency for the yield on long-term Treasuries to rise. (Presumably in a world where markets aren’t segmented demand for Treasuries is fairly elastic and shifts into other financial assets quash this effect.)

In short, a world where safe assets trade in segmented markets may be one where implementing monetary policy using the interest rate as a policy tool is particularly difficult. Can short-term and long-term safe assets become segmented markets as well? Given arbitrage, it’s hard to imagine how this is possible.

These thoughts are, of course, motivated by the behavior of Treasury yields following the Federal Reserves 25 bp rate hike in December 2015.fredgraph