Two times zero is zero, which leaves a lot of people scratching their heads about the acquisition of Chrysler, the troubled US carmaker, by Cerberus, the private equity group. Buy-out groups often double the return on equity of companies they acquire simply by loading on more debt. In this case, Cerberus has nothing to double because Chrysler is losing money.

Low interest rates and global liquidity have caused a wave of buy-outs, even in industries that private equity groups traditionally shun. Even airlines and automotive companies are now targets despite their thin margins, vulnerability to economic downturns and, in the US, large healthcare liabilities. Even by these standards, the deal with DaimlerChrysler is ambitious.