Emergency communication system
161 people were killed and at least 990 injured when an EF5 multiple-vortex tornado hit Joplin, Missouri. Because Joplin is located in a tornado-heavy area of the country, many people considered the tornado sirens routine and ignored them. Instead, many residents waited until they received confirmation from another, non-routine, source, such as seeing the tornado, a radio or TV report, or hearing a second siren. In the aftermath, an assessment team recommended that emergency warnings take risk perception into account to convey a sense of urgency. NOAA Officials are considering ways to change the warning system to distinguish smaller tornadoes from more deadly ones.
Tornado records
Similar to fatalities, damage (and observations) of a tornado are a coincidence of what character of tornado interacts with certain characteristics of built up areas. That is, destructive tornadoes are in a sense "accidents" of a large tornado striking a large population. In addition to population and changes thereof, comparing damage historically is subject to changes in wealth and inflation. The 1896 St. Louis–East St. Louis tornado on May 27, incurred the most damages adjusted for wealth and inflation, at an estimated $2.9 billion (1997 USD). In raw numbers, the Joplin tornado of May 22, 2011 is considered the costliest tornado in recent history, with damage totals near $2.8 billion (2011 USD). Until 2011, the "Bridge Creek-Moore tornado" of May 3, 1999 was the most damaging.