Measuring Death
You’d think the ultimate example of simplicity in measurement would be mortality rate.
Count up the dead people – they aren’t hard to catch. Divide by the total number of people you had when you started.
Done.
It’s not super complicated but it is slightly more complicated than that.
First of all, how do you figure the number of people in the population? The population changes all of the time. People are born, people die. So to compute annual mortality rate you use this formula
Total number of deaths from all causes in 1 year X 1,000
Number of persons in the population at midyear
(You can also use per 10,000, 100,000 or million. There is nothing magic about the number 1,000).
You also may want to compute mortality for certain groups, for example, by age. You would then calculate the age-specific mortality rate For example, if we want to know the mortality rate of children aged 15 and under it would be
Number of deaths from all causes in 1 year of children under 16 x 1,000
Number of children under 16 in the population at midyear
There is also cause-specific mortality rate
Number of deaths from specific disease in one year x 1,000
Number of persons in the population at midyear
CASE-FATALITY is a very different thing than mortality rate. Case-fatality is
Number of individuals dying during a period after disease onset X 100
Number of individuals with the disease
For example, the annual mortality rate from measles in 1971-1975 was .17 per million
During that same period, the case fatality rate was about .1% or .98 per 1,000.
Think about that. One person out of 1,000 who got measles died.
Unfortunately, measles are making a comeback in the United States due to stupid bastards who don’t vaccinate their children. Whether this will translate to an increase in mortality rate remains to be seen. With only 644 cases in 2014, there hasn’t been a reported death – yet.
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