If you would like to create a "Most Improved" Table, there is a feature to compare 2 competitions which will compare 2 date ranges, calculate the difference and show the Improvement Percentage and Rank by Most Improved.

Set up 2 competitions for the selection and criteria needed. One for first Year and one for the second Year, say Improvers 2017 and Improvers 2018.
First, make sure you calculate and display the Improvers 2017.
Then on the Improvers 2018, the last option of the "Rules for Competition", set to compare Improvers 2017.

There will now be 3 columns, Improvement, Current Average, Previous Average.

The Improvement will be calculated as a percentage of the ( Current Average - Previous Average  ) / Previous Average,

e.g. Current 51.00, Previous 48.50, Improvement = (51.00 - 48.50) = 2.50 as a percentage ( 2.50 / 48.50 ) * 100 = 5.15

If you have a Best Competition, then the Improvement will be calculated as a percentage of the ( Current Total - Previous Total  ) / Previous Total,