From the US Fed to the ECB and the Bank of Japan, central bankers and their macro prudential risk analysts have been sounding alarm bells on the global corporate bonds markets.  With a good reason: during the current recovery period, for the first time since 1954, the average yields on corporate AAA- and BAA-rated debt have fallen below 4.15 and 5.15 per cent, respectively. As of the end of August, seasoned (maturity- and issue-adjusted) US corporate yields have fallen to 3.2 per cent for the AAA-rated debt and to 4.2 per cent for the BAA-rated debt. The same is happening…