Federal debt crossed $18 trillion at the end of last year, but most of the increase in marketable securities has ended up in central banks (including the Federal Reserve) and the amount that’s available to investors as long-term investments is a surprisingly small chunk of the whole amount. Zoltan Pozsar, director of US economics research at Credit Suisse, has broken down who exactly owns what in a recent presentation to show where all that debt had ended up and finds that only 6% is available for investors who want to buy and hold Treasury bonds. The Fed holds nearly a…