So what is behind this massive rally? Certainly it has been helped by a wave of liquidity from near-zero interest rates and quantitative easing. But a more important factor fuelling this asset bubble is the weakness of the US dollar, driven by the mother of all carry trades. The US dollar has become the major funding currency of carry trades as the Fed has kept interest rates on hold and is expected to do so for a long time. Investors who are shorting the US dollar to buy on a highly leveraged basis higher-yielding assets and other global assets are not just borrowing at zero interest rates in dollar terms; they are borrowing at very negative interest rates – as low as negative 10 or 20 per cent annualised – as the fall in the US dollar leads to massive capital gains on short dollar positions.
(...) Central banks in Asia and Latin America are worried about dollar weakness and are aggressively intervening to stop excessive currency appreciation. This is keeping short-term rates lower than is desirable. Central banks may also be forced to lower interest rates through domestic open market operations. Some central banks, concerned about the hot money driving up their currencies, as in Brazil, are imposing controls on capital inflows. Either way, the carry trade bubble will get worse: if there is no forex intervention and foreign currencies appreciate, the negative borrowing cost of the carry trade becomes more negative. If intervention or open market operations control currency appreciation, the ensuing domestic monetary easing feeds an asset bubble in these economies.http://www.rgemonitor.com/roubini-monitor/257912/mother_of_all_carry_trades_faces_an_inevitable_bust