One of the traditional arguments for higher common equity requirements is that it increases the shareholders’ “skin in the game” and thereby creates an incentive to be more diligent and conservative in managing risk.
This principle is true up to a point but I believe more common equity mostly generates this desirable risk management incentive when the extra skin in the game (aka capital) is addressing a problem of too little capital. It is much less obvious that more capital promotes more conservative risk appetite for a bank that already has a strong capital position.
In the “too little” capital scenarios, shareholders confronted with a material risk of failure, but limited downside (because they have only a small amount of capital invested), have an incentive to take large risks with uncertain payoffs. That is clearly undesirable but it is not a fair description of the risk reward payoff confronting bank shareholders who have already committed substantial increased common equity in response to the new benchmarks of what it takes to be deemed a strong bank.
The European Systemic Risk Board published some interesting research on this question in a paper titled “Has regulatory capital made banks safer? Skin in the game vs moral hazard” . I have copied the abstract below which summarises the key conclusions.
Abstract: The paper evaluates the impact of macroprudential capital regulation on bank capital, risk taking behaviour, and solvency. The identification relies on the policy change in bank-level capital requirements across systemically important banks in Europe. A one percentage point hike in capital requirements leads to an average CET1 capital increase of 13 percent and no evidence of reduction in assets. The increase in capital comes at a cost. The paper documents robust evidence on the existence of substitution effects toward riskier assets. The risk taking behavior is predominantly driven by large and less profitable banks: large wholesale funded banks show less risk taking, and large banks relying on internal ratings based approach successfully disguise their risk taking. In terms of overall impact on solvency, the higher risk taking crowds-out the positive effect of increased capital.
I have only skimmed the paper thus far and have reservations regarding how they measure increased risk. As I understand it, the increased riskiness the analysis measures is based on increases in average risk weights. It was not clear how the analysis distinguished changes in portfolio riskiness from changes in the risk weight measure. That said, the overall conclusions seem intuitively right.