Complexity of banks can have important ramifications for the performance and the risks of the banking system. Financial sector reforms that were implemented in the past decade have thus aimed to reduce and to better manage the risk implications of bank complexity. Yet, surprisingly little is known about changes in complexity across countries, its drivers, and its effects. The International Banking Research Network (IBRN) used data and analytical advances to generate rich cross-country insights on the complexity and riskiness of banking organizations. The initiative has four key findings. First, the largest banks in countries tend to be the more complex ones. Yet, even controlling for size, there is substantial diversity across banking organizations in terms of complexity choices. Second, over the past decade, banking organizations have tended to reduce complexity by limiting the number of affiliates in both domestic and foreign locations. Generally, however, complexity patterns are fairly persistent. Third, regulatory changes can alter both banking organization complexity and the associated risk profiles. Fourth, the link between complexity and risks involves trade-offs: diversification benefits and reductions in liquidity risk may weigh against agency problems, monitoring costs, and systemic risk contributions arising from higher complexity.

Bank holding companies (BHCs) can be complex organizations, conducting multiple lines of business through many distinct legal entities and across a range of geographies. While such complexity raises the costs of bank resolution when organizations fail, the effect of complexity on BHCs’ broader risk profiles is less well understood. Business, geographic, and organizational complexity can engender explicit tradeoffs between the agency problems that increase risk and the diversification, liquidity management, and synergy improvements that reduce risk. The balance of outcomes may depend on the strength of bank governance. We test these conjectures using data on large U.S. BHCs for the 1996–2018 period. Business, geographic, and organizational complexity provide diversification benefits and some reduced idiosyncratic and liquidity risk exposure. All forms of complexity tend to increase BHC systemic risks. A regulatory tightening focused on complexity reduced organizational complexity, while also curtailing systemic risk but increasing liquidity risk.