Calculate % Change
When you calculate percent change, you are calculating the change in numerical values over time. Calculating change as a percentage is a form of normalization, which makes it especially useful for comparing areas that are not uniform in size or population.
Note:You can also calculate percent change using the View Data Table window.
Example
A crime analyst is studying the effects of a city's crime reduction strategy. Calculate % Change can be used to determine the effectiveness of the strategy in different districts using the crime rate before the program started and the crime rate after the program's implementation.
Usage notes
Calculate % Change can be found using the Action button 
under How has it changed? in the Find Answers tab. The input layer can be a point, line, or area layer.
Two number fields must be chosen as the initial value and the final value. The number fields will be used in the equation: (final_value-initial_value)/initial_value*100
Calculate % Change adds a new rate/ratio field to the input layer. You must include a new field name to run the calculation.