The message beneath the yen intervention

The U.S. and Japanese governments have acted together to try to prop up the value of the yen on global currency markets. The way they did it contains a clue about U.S. goals — and has some worrying implications for global markets. The big picture: Headline indicators have been steady across global financial markets this summer. Yet there are some signs of strains beneath the surface, particularly in the form of rising long-term borrowing costs at a time of elevated debt worldwide. The U.S.…