On VoxEU, Charles Calomiris and Matthew Jaremski discuss the origins of bank liability insurance. They argue that it is redistribution, not the aim to boost efficiency, which explains a lot of the action.

… there are two theoretical approaches to explaining the creation and expansion of deposit insurance. The first is an economic approach grounded in potential efficiency gains from limiting bank runs (i.e. the public interest motivation). The second is a political approach grounded in the rising power of special interest groups that favoured insurance as a means to access subsidies (i.e. the private interest motivation).

… Because insurance reduces the incentive for market discipline, it may increase fundamental insolvency risk … whether, on balance, bank liability insurance reduces or increases risk … is an empirical question. Economic theories of liability insurance only make sense on economic grounds if the gains from liquidity risk reduction tend to exceed the moral hazard or adverse selection costs from reduced market discipline.

… Political models seek to explain why liability insurance may be chosen to favour certain groups in society even when it imposes large costs on society in the form of higher systemic risk for banks. In this context, liability insurance needs to be understood as part of an equilibrium political bargain achieved by a winning political coalition. …

… we review empirical evidence about, first, which factors are shown to be instrumental in creating bank liability insurance; and second, evidence about the consequences of passing insurance … We find that political theories are much more consistent with both sets of evidence.

… the historical push for liability insurance in the US came from a coalition of small rural bankers and landowning farmers …

Worldwide, bank liability insurance remained a unique (and controversial) policy choice of the US until the late 1950s, but it spread rapidly throughout the world in recent decades …

Like the adoption of liability insurance in the US, the recent global wave of legislation creating and expanding insurance can also be traced to political influences. …

The expansion of liability insurance has been generally associated with reductions in banking system stability …

The political theories of liability insurance point to a major political advantage. It provides an effective means for a government to supply hard-to-trace subsidies to particular classes of bank borrowers … agricultural borrowers or urban mortgage borrowers …

Liability insurance can create a subsidy for banks (which they can pass through, in part, to borrowers) only if prudential regulation and supervision permit banks to take risks at the expense of the insurer. Thus, lax regulation and supervision are an important part of the political bargain that allows liability insurance to deliver subsidies to banks and targeted borrowers. …