I'm not convinced averages should be used at all.
'Average is a very vague term. Mathematically, there are 3 types of average -
1. Mean. This is found by adding up all of the numbers the you have and dividing it by the number of numbers. This is what most people think of as 'average'.
2. Median. The median is the number in the middle, when all the numbers are placed in order of magnitude.
3. Mode. The mode is the number in a set of numbers that occurs the most.
Personally, I think there is value in looking at both short and long term average (mean) data. Is a trend recent, or has it been occurring over a long period? If it has been occurring over a long period, how has that trend varied over that period? Is any rate of change faster now or was it faster in the past?
We then start getting into statistical data. Here, we have to be very careful, because statistics can be manipulated to say what you want.
A funny example of this comes from many years ago when the Rugby competition was 'The Five Nations'. England had finished top with Wales in fourth place. A Welsh lad working with us stated -
'Wales finished fourth, while all England could manage was fifth from bottom'.
Statistically correct, but for anyone not aware of the competition, it totally skews the result.
All I know, is at the moment I'm much too hot!
Kevin