The deadly plot unrealized. The heart attack not had. The truth is that the successes of both national security and public health often pass by unnoticed. Failures are tallied in fatalities. But assessing the social value of programs by counting the number of people who do not die, such as people saved by detecting a bomb or by new food labeling laws, can make effectiveness tough to measure.

The matter is further obscured by the nature of the threats they aim to fend off. Especially since the 9/11 attacks, security threats often loom larger in the collective national consciousness than health threats, although the chances of dying in a plane crash (of any kind), for instance, is about one in 20,000, whereas the odds of dying from a stroke are about one in 23—with the bulk of strokes likely being preventable. Disparate odds of this order are true of most security versus health risks.

So, how is the federal government spending money to stave off deaths from bombings and bugs alike? And does that spending reflect the relative risks of health threats versus security threats? Here is a glance at the budgets of the U.S. Department of Homeland Security (DHS), which is charged with terrorism prevention, cyber security and immigration enforcement, among other things, and the U.S. Centers for Disease Control and Prevention (CDC), which helps to fight infectious and chronic diseases, prevent injury and improve other health areas.

For the 2012 fiscal year, the DHS requested $57 billion in funding from the federal government, promising to have cut more than $800 million from administrative inefficiencies (which they plan to divert to "strengthen mission critical activities," according to the department's budget overview). The CDC requested $11.3 billion for 2012, and said that it includes some $100 million trimmed from administrative costs. (The CDC is part of the Department of Health and Human services, which also runs Medicare and Medicaid, as well as the Food and Drug Administration, the National Institutes of Health and other wellness-related programs; it requested $892 billion for its 2012 budget.)

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Given the greatly different natures of the two fields—security and preventive health—in how they report data and their goals, it is difficult to devise a measure of their comparative efficacy. By many counts, preventive health funds are cited as paying off some five times in saved medical costs per every dollar invested, whereas, a similar savings multiplier is not advanced regarding security funds. Likewise, it is also challenging to estimate the dollars per life saved for the various approaches to security and preventive health.

For one pair of researchers, however, the algebra is actually quite clear. For the more than $1 trillion the U.S. has spent on domestic security in the past decade to be justified in terms of lives saved, counterterrorism efforts would need to "have successfully deterred, derailed, disrupted, or protected against attacks that would otherwise have resulted in the deaths of more than 3,000 people in the country every year, equivalent to experiencing attacks as devastating as those on 9/11 at least once a year or 18 Oklahoma City bombings every year," the researchers wrote in the August issue of Homeland Security Affairs.

"Even if all of the terrorist plots exposed since 9/11 in the United States had been successfully carried out, their likely consequences would have been much lower," John Mueller, chair of National Security Studies at Ohio State University, and Mark Stewart, director of the Center for Infrastructure Performance and Reliability at The University of Newcastle in Australia, noted in their analysis. Although much security work is secretive, thus some thwarted attacks might remain undisclosed, based on public information, the "enhanced expenditures have been excessive…[even though] there are emotional and political pressures on the terrorism issue," they concluded.

The relative levels of security versus health spending on preventable deaths might however, make sense from a psychological perspective. Researchers who study risk perception have found that people tend to assess risk to themselves differently than they do risks to the broader population—even when they know the hard, relative numbers. "Riskiness is based on perception rather fact," Clinton Jenkin, a researcher at the University of New Hampshire, wrote in a 2006 paper published in Homeland Security Affairs.

So although the money spent on different prevention methods might not map out onto the available data, it might show more where our own—culture-driven or innate—fears lie. A lifetime of exposure to unhealthy foods or low levels of exercise has perhaps dulled the dread of a losing battle with heart disease (the leading cause of death in the U.S.), but lingering anxieties about a one-in-a-million-type terrorist attack keep funds—and, as no small consolation, jobs—flowing more freely to domestic security. And who is to say that that extra $1 million for domestic security is not going to supply the extra eyes—or canine nose—that detects the next nefarious plot? The research has already shown what that money would do in a preventive health setting, so perhaps the unknown in the terrorist equation has fueled a fire of uncertainty that keeps those funds flowing.

Interactive by Krista Fuentes