Jan-Peter Siedlarek

This paper proposes a parsimonious model of network formation with introductions in the presence of intermediation rents. Introductions allow two nodes to form a new connection on favorable terms with the help of a common neighbor. The decision to form links via introductions is subject to a trade-off between the gains from having a direct connection at lower cost and the potential losses for the introducer from lower intermediation rents. When nodes take advantage of introductions, stable networks tend to exhibit a minimum amount of clustering. At the same time, intermediary nodes have incentives to protect their position, and stable networks can exhibit nodes exploiting structural holes, that is, bridges across otherwise unconnected parts of the network earning intermediation rents.

Understanding banks’ responses to capital regulation is essential for regulators to use this key tool of modern banking regulation effectively. We study how and when US banks responded to changes to the way capital ratios are measured, changes that were introduced as part of the adoption of Basel III. We find that small banks — those below USD 10bn — responded neither before nor after the release of the new rules to the change in measured capital they experienced under the new rules. In contrast, we show that regional banks — those with total assets between USD 10bn and USD 50bn — adjusted their capital ratios to partially compensate for the changes resulting from the new rules: On average, if a bank’s capital ratio when measured under the new rules was lower than under the old rules, then the bank took steps to increase its capital ratio, compared to a bank whose capital ratio did not change with the new rules. This adjustment took place prior to the publication of the specific language applicable to US banks, suggesting that the changes were largely expected by that time. Both groups of banks responded in the periods following the release of the new US rules in relation to their exposure to mortgage servicing rights, suggesting that the severe treatment of this asset class was not expected. The bank responses we estimate take place well before the Basel III rules started to come into force after 2014, emphasizing the importance of policy announcements in shaping bank behavior.

This paper proposes a parsimonious model of network formation with introductions in the presence of intermediation rents. Introductions allow two nodes to form a new connection on favorable terms with the help of a common neighbor. The decision to form links via introductions is subject to a trade-off between the gains from having a direct connection at lower cost and the potential losses for the introducer from lower intermediation rents. When nodes take advantage of introductions, stable networks tend to exhibit a minimum of clustering. At the same time, intermediary nodes have incentives to protect their position, and stable networks can exhibit bridges across otherwise unconnected parts of the network earning intermediation rents.

High levels of clustering—the tendency for two nodes in a network to share a neighbor—are ubiquitous in economic and social networks across different applications. In addition, many real-world networks show high payoffs for nodes that connect otherwise separate network regions, representing rewards for filling “structural holes” in the sense of Burt (1992) and keeping distances in networks short. This paper proposes a parsimonious model of network formation with introductions and intermediation rents that can explain both these features. Introductions make it cheaper to create connections that share a common node. They are subject to a tradeoff between gains from shorter connections with lower search cost and losses from lower intermediation rents for the central node. Stable networks are shown to have high levels of clustering at the same time that they permit substantial intermediation rents for nodes bridging structural holes.

The effect of regulations on the banking sector is a key question for financial intermediation. This paper provides evidence that merger control regulation, although not directly targeted at the banking sector, has substantial economic effects on bank mergers. Based on an extensive sample of European countries, we show that target announcement premia increased by up to 16 percentage points for mergers involving control shifts after changes in merger legislation, consistent with a market expectation of increased profitability. These effects go hand-in-hand with a reduction in the propensity for mergers to create banks that are too-big-to-fail in their country.

We highlight that convergence in repeated averaging models commonly used to study cultural traits or opinion dynamics is not equivalent to convergence in Markov chain settings if transition matrices are time-varying. We then establish a new proof for the convergence of cultural traits in the model of Panebianco (2014) correcting the existing proof. The new proof provides novel insights on the long-run outcomes for inessential individuals. We close with a discussion of conditions for convergence in repeated averaging models with time-varying transition matrices.

We find that stricter merger control legislation increases abnormal announcement returns of targets in bank mergers by 7 percentage points. Analyzing potential explanations for this result, we document an increase in the pre-merger profitability of targets, a decrease in the size of acquirers, and a decreasing share of transactions in which banks are acquired by other banks. Other merger properties, including the size and risk profile of targets, the geographic overlap of merging banks, and the stock market response of rivals appear unaffected. The evidence suggests that the strengthening of merger control leads to more efficient and more competitive transactions.

We find that stricter merger control legislation increases abnormal announcement returns of targets in bank mergers by 7 percentage points. Analyzing potential explanations for this result, we document an increase in the pre-merger profitability of targets, a decrease in the size of acquirers, and a decreasing share of transactions in which banks are acquired by other banks. Other merger properties, including the size and risk profile of targets, the geographic overlap of merging banks, and the stock market response of rivals appear unaffected. The evidence suggests that the strengthening of merger control leads to more efficient and more competitive transactions.

I study intermediation in networked markets using a stochastic model of multilateral bargaining in which players compete on different routes through the network. I characterize stationary equilibrium payoffs as the fixed point of a set of intuitive value function equations and study efficiency and the impact of network structure on payoffs. There is never too little trade but there may be an inefficiency through too much trade in states where delay would be efficient. With homogeneous trade surplus the payoffs for players that are not essential to a trade opportunity go to zero as trade frictions vanish.

We explain persistent differences in cultural traits of immigrant groups with the presence of community leaders. Leaders influence the cultural traits of their community, which have an impact on the group's earnings. They determine whether a community will be more assimilated and wealthier or less assimilated and poorer. With a leader, cultural integration remains incomplete. The leader chooses more distinctive cultural traits in high-productivity environments and if the community is more connected. Lump-sum transfers to immigrants can hinder cultural integration. These findings are in line with integration patterns of various ethnic and religious groups.

On average, capital ratios of US banks increased between 2009 and 2012, plateauing before the Basel III rules came into force, but timing varied by bank size and capitalization.

We compare two types of models used to predict the spread of the coronavirus, both of which have been used by government officials and agencies. We describe the nature of the difference between the two approaches and their advantages and limitations. We compare examples of each type of model—the University of Washington IHME or “Murray” model, which follows a curve-fitting approach, and the Ohio State University model, which follows a structural approach.

Many models have been developed to forecast the spread of the COVID-19 virus. We present one that is enhanced to allow individuals to alter their behavior in response to the virus. We show how adding this feature to the model both changes the resulting forecast and informs our understanding of the appropriate policy response. We find that when left to their own devices, individuals do curb their social activity in the face of risk, but not as much as a government planner would. The planner fully internalizes the effect of all individuals’ actions on others in society, while individuals do not. Further, our simulations suggest that government intervention may be particularly important in the middle and later stages of a pandemic.

Many of the models used to track, forecast, and inform the response to epidemics such as COVID-19 assume that everyone has an equal chance of encountering those who are infected with a disease. But this assumption does not reflect the fact that individuals interact mostly within much narrower groups. We argue that incorporating a network perspective, which accounts for patterns of real-world interactions, into epidemiological models provides useful insights into the spread of infectious diseases.

One potential threat to a stable financial system is the phenomenon of contagion, where a risk that is ordinarily small becomes a problem because of the way it spreads to other institutions. Researchers have investigated multiple channels through which contagion might occur. We look at two--banks borrowing from each other and banks holding similar types of assets--and argue that the latter is a potential source of systemic risk. We review recent data on asset concentrations and capitalization levels of the largest US banks and conclude that the overall risk from this particular contagion channel is at present likely limited.

This Commentary discusses the implications of merger control policy on merger activity in the banking sector, drawing on an analysis of the European banking sector during a period in which stricter merger policies were being introduced. It identifies several changes to the bank mergers taking place after the introduction of the stricter policies that are consistent with higher expected returns for shareholders and more procompetitive transactions. The evidence suggests that the new merger policy was successful in preventing mergers that are excessively anticompetitive, while it also led to banks’ finding mergers that are expected to deliver greater efficiency.