Research in Progress Context, Bayesian Updating and Cry Wolf Phenomenon in Hurricane Evacuation Behavior: A Panel Study Pallab Mozumder, Hugh Gladwin and Fang Zhao Florida International University Miami, Florida

Background Dissemination of hurricane forecasts, public risk perception and evacuation decision-making are intertwined complex processes. Willoughby et al. (2007): Steady improvement in hurricane forecasts faces diverse challenges (better forecasting of intensity, wind, rain & sea-state remain problematic). A household ’ s decision to evacuate is a self-protective behavior implemented in a multidimensional context (MacGregor et al. 2007).

Updating Risk Perception In unusual situations, preferences for risk aversion are learned, and converge through a process of repetition & experience (Plott 1996). Bayesian Updating: people incorporate new information in updating their risk perception. A Bayesian agent maximizes expected utility given a subjective prior over possible outcomes (Kreps 1988). In updating Risk Perception, not only past events, but surrounding contexts & socio-economic factors may also influence the belief formation and evacuation decision. Updating can take place through both upward & downward adjustment of risk perception (Upward: Close Call, Near Miss; Downward: Cry Wolf, False Alarm etc.).

A Behavioral Model of Evacuation Decision Making

Predicting Hurricane Evacuation Behavior

Data In 2006 a sample of residents of coastal Alabama, Mississippi and Louisiana who were first interviewed after Hurricane Ivan (2004) were re- interviewed about their evacuation experiences with Hurricane Katrina (2005). The unique panel data constructed through repeated surveys allows us to closely monitor how prior experience and risk perceptions affect subsequent evacuation behavior.

Hurricane Ivan (Sept, 2004) Hurricane Katrina (Aug 2005)

Ivan and Katrina Evacuation Evacuation rates for Ivan were almost 50%. Many Louisiana respondents reported long evacuation traffic delays for a hurricane that eventually did not hit the area. Such experiences can be seen as a "cry wolf" phenomenon that may have negatively affected evacuation behavior in the wake of hurricane Katrina in However, survey evidence does not tend to provide much support for “ cry wolf ” effect. But other factors related to forecast information, timing of the information received and time available to evacuate tend to play more important roles.

Ivan interviews

Geographic Variations of Household Evacuation

Temporal Variation of Household Evacuation: Hurricane Ivan Mon: 13 th Sept, Tues: 14 th Sept, Wed: 15 th Sept

Katrina Evacuation Aug 26Aug 27Aug 28

Table 1. Comparison Between Ivan and Katrina Evacuation (Same Households) Freq.Percent Hurricane Ivan Yes, Evacuated No, Did Not Evacuate Total Hurricane Katrina Yes, Evacuated No, Did Not Evacuate Total

Ivan & Katrina: Comparing Hurricane Characteristics Hurricane (Year) Landfall in State Category During Landfall Reported Deaths in US Normalized Economic Damage (Bill $, 2005) Ivan (04)FL Katrina (05)FL, LA, MS Source: NOAA Hurricane History and Pielke et al. (2008)

Closing Comments People with past experiences of unneeded evacuations were not less likely to evacuate (i.e., not enough support for “ cry wolf ” effect). Other factors related to forecast information, timing of the information received, time available to evacuate may play more important roles. Our ongoing research is focusing on why people tend to adjust their risk perception upward rather than downward (how other factors interact) in their evacuation decisions.

Thank You Acknowledgements: Hurricane Alliance – NOAA National Science Foundation Drew Berry & Associates