Extension and combination of economic input output models for assessing critical infrastructure system interdependencies

Unmanaged interdependency has become one of the significant factors that could hamper the reliable supply of services from various economic sectors. Critical infrastructure sectors, whose secured service provision is extremely crucial for the healthy operation of the entire economy, are facing evident interdependency related risk more than ever. The difficulty in studying system interdependency is mainly due to the scale of these systems and the complexity of the interconnections among them.; In the first part of the research, I propose methods that can systematically evaluate the dependency among economic sectors. Motivated by the effective representation of monetary connections among different sectors using an economic input-output model and the demand reduction inoperability model proposed by Haimes, I augment these existing models by showing the existence of two-way disruption propagation modes and propose an approach to evaluate system vulnerability caused by interdependency by integrating the total supply chain disruption effects derived from the two interdependency models. Based on the output from the two interdependency models, the vulnerability and influence of these infrastructure systems can be evaluated and compared through a proposed "vulnerability profile" and "influence profile".; In the second part of the research, I investigate how the economic model output can facilitate the quantification of the impact on the real operational practice of these infrastructure systems, such as when the full operational capacity starts to drop. Assessment of dependency caused interruption that is often affected by a set of different factors on the operational practice is of great interest for system managers. Through regression analysis, I demonstrate that the impact on the operational status of a large portion of the investigated infrastructure sectors is closely related to the financial losses that these sectors have to bear. The interruption of the operational status is due to the unavailability of sufficient supply while the financial loss mainly comes from the unimplemented productions. Through regression analysis, I demonstrate that the impact on the operational status of a large portion of the infrastructure sectors under investigation due to unavailability of enough supply is closely related to the financial losses these sectors have to bear because of the unimplemented productions. That is, in a lot situations, the financial significance resembles the criticality of the supply sector to the affected system. By utilizing a simulation-based sensitivity analysis approach, I illustrate that the resilience of an interconnected economic system formed by selected infrastructure systems can be improved effectively by adjusting the resilience property of individual sectors. The analysis shows the existence of optimal risk preparation capacity at intermediate systems that can maximally reduce the losses at involved systems and minimize the resources that are required. This is extremely important for risk prioritization given there are limited resources.