1. The Marginal Value of Weather Warning Systems Benjamin M. Miller University of California, San Diego Not-so ^

2. What causes disaster deaths?

4. U.S. Tornado Warning History & Infrastructure First successful tornado warning – Tinker Air Force Base, Oklahoma City, 1948 – National Weather Service begins Watch/Warning system in 1953 Outdoor Warning Sirens – Originated as air-raid sirens in WWII. NOAA Weather Radio/SAME Receiver – NOAA now has over 1,000 transmitters which cover most of the U.S. Television/Radio – Warnings issued through the EBS/EAS Commercial Mobile Alert System

5. Research Question Do warning systems causally reduce deaths and injuries?  How much? NOAA radio transmitters

6. In the Literature Responsiveness to warning systems is mostly case studies:  Balluz et. al (2000) Survey of 146 individuals following March 1, 1997 tornadoes in Arkansas  Liu et. al (1994) Survey roughly 194 households in two Alabama areas after tornado warnings. “In the area without sirens, only 28.9% of 194 respondents heard a tornado warning of these, 73.2% first received the warning from radios or television. In the area with sirens, 88.1% of 193 respondents heard a warning, and 61.8% first received the warning from a siren.” These are great, but the counter-factual is not clear. How would people have fared without a particular warning system?

7. Identifying Variation Transmitter broadcast area – Very endogenous: correlated with population density and other factors correlated with the number of fatalities and injuries. – Could control for some but not all of these factors Date of transmitter installation – Compare tornado outcomes between counties which both eventually get transmitter coverage – Compare tornado outcomes within the same county before/after transmitter installation – In either case, can’t control for concurrent regional changes

8. Identifying Variation Compare tornado outcomes between similar counties which both eventually get transmitters  Worry the date of transmitter installation is correlated with a county's potential tornado injuries and fatalities Can control for observed differences If areas receiving transmitters first have more deaths/injuries for an unobserved reason, the value of transmitters will be underestimated Compare tornado outcomes within the same county before/after transmitter installation  Worry the date of transmitter installation is correlated with trends in a county's potential tornado injuries and fatalities?  Sacrifice external validity Requires restricting sample to areas with pre- and post-installation single- county tornadoes, at least one of which a non-zero outcome

9. Data Tornado Characteristics  57,120 recorded tornadoes from 1950-2012  Counties passed through  (Enhanced) Fujita scale  Death, injuries, and sometimes damages State-tornado level County Characteristics  Which transmitters broadcast in the county, date of installation/deactivation  County-level population data from Decennial Census, with annual intercensal estimates  State-decade-level housing types (ex. mobile, detached house, etc.) from the Historical Census of Housing

10. Number of Tornadoes, 1950 - 2012

11. Number of EF3+ Tornadoes, 1950 - 2012

14. Number of NOAA Transmitters: Jan 1, 1950

15. Number of NOAA Transmitters: Jan 1, 1960

16. Number of NOAA Transmitters: Jan 1, 1970

17. Number of NOAA Transmitters: Jan 1, 1980

18. Number of NOAA Transmitters: Jan 1, 1990

19. Number of NOAA Transmitters: Jan 1, 2000

20. Number of NOAA Transmitters: Jan 1, 2010

21. Empirical Analysis log(Fatalities/Injuries/Property Damage i ) = β[Transmitter Coverage] i + γ[Controls i ] + ε i Transmitter Coverage  One or more transmitters broadcasting over the tornado path  β is the percent change attributed to transmitter coverage Controls  Population, Date of transmitter installation, (Enhanced) Fujita Scale, Path length, State Fixed Effects, Month & Year Fixed Effects, Distribution of home types  Could add income, county size, demographics...  County FE Count Data  OLS biased, use Poisson regression

26. Conclusion Significant causal reduction in injuries and fatalities  On average, about 30% reduction Most causal prevention of deaths/injuries comes from higher EF Scale tornadoes Other stuff:  Any benefit from multiple transmitters?  Benefits decline over time as replaced by new technology? Importance for choosing optimal investment within and across warning systems

27. Thank you! Any and all comments/suggestions are completely welcome.