Investment banks have reined in their worst pay excesses. But inconsistent enforcement of bonus rules in the United States and Europe means some are still getting away with bad behaviour. If banks and regulators can't agree common standards, they risk another political backlash.

It's almost 18 months since the world's regulators agreed a common set of principles for bank pay. But the interpretation of those standards has been far from consistent. While the U.S. Federal Reserve has issued the institutions it regulates with broad guidelines, the European Union has passed a detailed directive, including a requirement that a proportion of any bonus should be paid in the form of contingent capital. Add in one-off levies like the UK bank payroll tax, and it's not hard to see why banks are struggling for a common approach.

Investment banks have cleaned up their act to some extent. Most bonuses now include some deferred payment, often in the form of stock. This aligns bankers' incentives with those of shareholders, and discourages them from taking short-term risks that may blow up in a year or two. Multi-year guaranteed bonuses have almost entirely disappeared.

However, there are plenty of signs that some banks are still ignoring the spirit of the new rules.