To give you a brief overview of the calculations used here with inflatR, let it be known that this site was not made geared towards accuracy of an estimation, but more so the technical aspects of producing such a website. Let it also be known that the estimation process will be refined as time goes on. The creater had a tight deadline to make, and bit off more than she could chew. :]
First, the user data is given a weight that is calculated by the amount of individual monthly expenses over monthly salary. Then the appropriate query is made off of the application's database to calculate the inflation rate of one expense parameter over two consecutive years. Last, the inflation rate multiplied by the weight of each expense parameter is summed to provide an overall rate between two years.
Unfortunately, due to the nature of the form, the user's monthly expenses are not exact. If one had a rental expense of $1650/month, a range is selected. The upper limit of that range is then selected to calculate the weight over salary. In the future, this limitation will corrected to allow for actual user input.
Also, due to the nature of the available data from the Bureau of Labor Statistics, not all regions have the same granular detail of items measured, nor is each region measured in the same time intervals. Because of this, the expense parameters are matched up with the highest-level of inflation series item measured by the BLS. For instance, if the user had monthly tuition expenses, it would fall under the broad bucket of "Education and communcation." While parameter selections might be refined, this is ultimately reliant on the data that the BLS provides. Perhaps additional/supplementary data can be pulled from other sources.
Lastly, if anyone has a better way to estimate inflation, as opposed to weighting expense inflation rates according to percentage of monthly salary, let's here it.
Enjoy.