Tornado shelters and the housing market

August, 2007

Mitigation against natural hazards often involves long‐lived, immobile investments. Home owners must be able to capture the present value of future benefits to equate the private and societal return on mitigation. The capitalization of mitigation into home prices thus is crucial for home owners to have a proper incentive for mitigation. We investigate the existence of a premium for tornado shelters using home sales in Oklahoma City, where the deadly tornado outbreak of 3 May 1999 and the Oklahoma Saferoom Initiative increased public awareness of tornado shelters. We find that a shelter increases the sale price of a home by 3.5% to 4% or approximately $4200 given the mean price of homes sold in 2005. The magnitude of the premium is plausible given that shelters retail for $2500–$3000 installed.

Tornado shelters and the manufactured home parks market

December, 2007

Manufactured or mobile homes represent a fast growing portion of the housing market but are particularly vulnerable to tornadoes. In the US over 40% of tornado fatalities occur in mobile homes even though they comprise about 8% of US housing units. We examine the market for tornado shelters in manufactured home parks in Oklahoma. Almost 60% of parks in the state have shelters, with 90% of the shelters underground. Parks with shelters are not concentrated in urban areas but spread across the state, with parks with shelters in 32 counties. We find that rents for lots in parks with shelters are 5–8% higher, which generates sufficient revenue to approximately pay for shelters, but the point estimate is statistically significant in only one specification.

Tornado Warnings, Lead Times, and Tornado Casualties: An Empirical Investigation

April, 2008

Conventional wisdom holds that improved tornado warnings will reduce tornado casualties, because longer lead times on warnings provide extra opportunities to alert residents who can then take precautions. The relationship between warnings and casualties is examined using a dataset of tornadoes in the contiguous United States between 1986 and 2002. Two questions are examined: Does a warning issued on a tornado reduce the resulting number of fatalities and injuries? Do longer lead times reduce casualties? It is found that warnings have had a significant and consistent effect on tornado injuries, with a reduction of over 40% at some lead time intervals. The results for fatalities are mixed. An increase in lead time up to about 15 min reduces fatalities, while lead times longer than 15 min increase fatalities compared with no warning. The fatality results beyond 15 min, however, depend on five killer tornadoes and consequently are not robust.

Manufactured home building regulations and the February 2, 2007 Florida tornadoes

September, 2008

The Department of Housing and Urban Development (HUD) and the state of Florida implemented new wind load and tie-down regulations for manufactured homes following Hurricane Andrew. This article examines the effect of the new regulations on the likelihood that occupants of mobile homes would survive a tornado. On February 2, 2007, three tornadoes struck central Florida, resulting in 21 deaths in Lake County, all in manufactured homes. The deaths occurred almost exclusively in homes rated as leveled by the county tax appraiser. Manufactured homes built to the new regulations, however, were significantly less likely to be leveled. Regression analysis finds that manufactured homes built to the post-Andrew requirements were 79% less likely to be leveled than homes built prior to the HUD Code in 1976, and 68% less likely to be leveled than homes built after 1976 but before the 1994 wind load regulations. Construction of all manufactured homes in the tornado paths to the wind load and tie-down requirements could have reduced fatalities by 70%.

Find the article at SpringerLink.

False Alarms, Tornado Warnings, and Tornado Casualties

October, 2009

This paper extends prior research on the societal value of tornado warnings to the impact of false alarms. Intuition and theory suggest that false alarms will reduce the response to warnings, yet little evidence of a “false alarm effect” has been unearthed. This paper exploits differences in the false-alarm ratio across the United States to test for a false-alarm effect in a regression model of tornado casualties from 1986 to 2004. A statistically significant and large false-alarm effect is found: tornadoes that occur in an area with a higher false-alarm ratio kill and injure more people, everything else being constant. The effect is consistent across false-alarm ratios defined over different geographies and time intervals. A one-standard-deviation increase in the false-alarm ratio increases expected fatalities by between 12% and 29% and increases expected injuries by between 14% and 32%. The reduction in the national tornado false-alarm ratio over the period reduced fatalities by 4%–11% and injuries by 4%–13%. The casualty effects of false alarms and warning lead times are approximately equal in magnitude, suggesting that the National Weather Service could not reduce casualties by trading off a higher probability of detection for a higher false-alarm ratio, or vice versa.

Tornado Fatalities and Mobile Homes in the United States

April, 2010

Fatalities from tornadoes have declined dramatically over the last century in the United States. Despite the overall reduction in tornado lethality, fatalities from mobile homes remain high. In fact, research suggests that the likelihood of a fatality in a mobile home is ten times or more than that in a permanent home. This study examines possible explanations of the mobile home tornado problem, including the potential for concentration of these homes in tornado prone states, the relation to Fujita Scale rating, and incidence during the day. We find that mobile home fatalities are concentrated in the Southeastern US, significantly more likely in weaker tornadoes, and occur disproportionately at night.

Economic and Societal Impacts of Tornadoes

March 15, 2011

For almost a decade, economists Kevin M. Simmons and Daniel Sutter have been studying the economic impacts and social consequences of the approximately 1,200 tornadoes that touch down across the United States annually. During this time, Simmons and Sutter have been compiling information from sources such as the National Oceanic and Atmospheric Administration and the U.S. Census in order to examine the casualties caused by tornadoes and to evaluate the National Weather Service’s efforts to reduce these casualties. In Economic and Societal Impacts of Tornadoes, Simmons and Sutter present their findings. This analysis will be extremely useful to anyone studying meteorology and imperative for anyone working in emergency disaster management.