By Radhika Sarin, Principal Researcher
How we assigned grades and ranks
How did Miami get an A in Population while Minneapolis got a C? We scored each indicator within a category using the same basic
formula. In the case of some categories, such as the Population category, there was only one indicator to score - population change. Other categories included
multiple indicators, so each indicator was scored and the sum of the indicators' scores was graded.
The formula that was used to score each indicator is as follows:
(City Y Value - Lowest City Value) = City Y Score
(Range of Values)
where
City Y Value = indicator value of city being scored
Lowest City Value = lowest indicator value in the data set
Range of Values = difference between the highest and lowest indicator values in the data set
Score = The higher the number, the better
Note: This formula is used when high values are "positive" while low values are "negative" (e.g. the number of Title X-funded
clinics). When high values are "negative" (e.g. infant mortality rates), the formula used to score indicator values is as follows:
1 - (City Y Value - Lowest City Value) = City Y Score
(Range of Values)
We applied this formula to every city. Then, we added up indicator scores within a category for each city. For example, the Public Safety category score
was the sum of the scores of violent crimes per 1000 persons and property crimes per 1000 persons. This total score was given a grade using a
normal distribution curve.
EXAMPLE: How we did the scores
Cities' final ranks are based on their total scores. The city with the highest score ranked first, the city with the second
highest score ranked second, and so on. All scoring and grading was done separately for the three city groups (Major, Independent, and Component).
Example: In order to determine the percent births to teens score for Greensboro, North Carolina (Independent city with
11.1% births to teens), the first step is to find the Independent city with the lowest value-this is Ann Arbor, Michigan, at 4.4%. Next, find the Independent
city with the highest value-this is Gary, Indiana, at 25.1%. Finally, use the following formula to determine Greensboro's score:
1 - (11.1 - 4.4) = 0.67
(25.1 - 4.4)
This indicates that Greensboro scored slightly better than the average (0.50) for all of the Independent cities that we studied. In fact, the average city
value for births to teens is 15%, and Greensboro's value of 11.1% is, indeed, lower than this value, giving it a higher than average score. Ann Arbor gets the
highest possible score of 1, while Gary gets the lowest possible score of 0.
