Understanding and Using Statistics
Risk is a commonly used term in health-related statistics to describe the
possibility of illness, injury, or death.
There are several ways to measure the risk of firearms injury and death.
The most common tool for measuring the risk of firearms violence is the rate. Rates related to gun violence are most commonly expressed as a number of deaths or injuries per 100,000 people. (They are sometimes expressed as another multiple of 10 such as: per 10,000, or per 1,000,000 people). For example:
In 1996 the U.S. rate of firearms death was 12.8 per 100,000.
This means that in 1996 nearly 13 out of every 100,000 Americans died in firearm-related violence.
The way to derive a rate is to take the number of deaths or injuries from guns in a group of people, divide by the total population of people in that group, and multiply by the number that will best express the risk. For example, to obtain the overall U.S. rate of firearm deaths:
(Number of firearm deaths in the U.S. in 1996 divided by the population of U.S. in 1996) X 100,000 = Rate per 100,000
Sometimes firearm-related death rates are age-specific. Age-specific death rates are the number of deaths per 100,000 population in a specified age group, such as 10 years to 14 years of age or 15 years to 24 years of age for a specified period. For example:
In 1996 the U.S. rate of firearms death among people aged 15 to 24 was 24.2 per 100,000.
Age-specific rates are very useful for describing the risk of gun violence because death and injury from guns is not consistent across the life span. As illustrated above, the age-specific rate of firearms death for people aged 15 to 24 is much higher than the overall U.S. rate. This means that people aged 15 to 24 are nearly twice as likely to be victims of firearms deaths than the overall U.S. population. To obtain the U.S. rate of firearm deaths among people aged 15 to 24:
Firearm deaths in the U.S. for people aged 15 to 24 in 1996 divided by Number of people aged 15 to 24 in the U.S. in 1996 X 100,000 = Rate per 100,000
Sometimes the rate is higher for one group than another even though the actual number of deaths or injuries is smaller. For example:
In 1996 there were 8,050 African-American males and 20,511 white males killed by firearms in the United States. In 1996 the U.S. firearm-related death rate among African-American males was 50.6 per 100,000 while the firearm-related death rate of white males was 19.0 per 100,000.
Even though the number of deaths was higher among white males, the rate of firearms death was higher among African-American males. The higher firearms death rate among African-American males indicates that, in 1996, more African-American males per 100,000 African-American males in the population were killed with guns than white males per 100,000 white males in the population. This is because the population of African-American males is much lower than white males (16 million versus 108 million in 1996). African-American males were more than two-and-a-half times as likely to be shot and killed than were white males. As this example illustrates, the number of firearm deaths is not as accurate a measure of risk as the rate of firearms death. Comparing rates (e.g. males versus females, youths aged 15 years to 19 years old versus the overall population) is the most accurate way to describe the impact of gun violence on various groups of people.
The second most common statistical tool for measuring the impact of firearms violence is a proportion. A proportion is expressed as a percentage of people affected by a variable out of a larger group. For example:
In 1996, 68 percent of all Americans who died in homicides were killed with firearms.
To calculate this proportion, take the number of people who died in homicides that were killed with firearms and divide by the number of people who died in homicides.
14,327 firearm-related homicides divided by
20,971 overall homicides = .68 x 100 = 68 percent