I think the best measure of productivity is results. Results that are relevant for you. If you are say in commission based sales then it’s how many sales you are generating.
A trap I see with productivity is that people often measure output. Like a productive day is one where they were in flow state, got a lot done and had minimal distractions. But what if all that work created no tangible result?
Let’s say you are planting trees. If one person plants 100 trees in 8 hours, and another plants 50 trees in 8 hours, you’d generally say that the first person was more productive. Even if the second person was in a flow state and had minimal distractions.
If measuring just output and not results, then consider 2 sales people. Both work for 8 hours going door-to-door selling. The first person knocks on 200 doors, and the second knocks on 50. It’s common to think the first person was more productive. But what if the first person got 0 sales and the second got 5 sales?
I see this kind of thing at work a lot. There is an element of self-deception often present with productivity. A productive day often means a lot of activity was completed. But it takes analysis to figure out if that activity was truly productive or not.
Output can sometimes be a good measure for productivity. Say you are a writer it might be good to have a target of how many words you write in a day. The measure of results - whether your book sells or not - might be so far down the track, activity could be the best thing to track. But then again it could be high or low quality writing.
I personally define productivity as the shortest distance between A and B. A being where you are now and B where you want to be. Say it’s a certain financial, fitness, or other goal, the most productive person is the one who gets there the fastest.
This could make the self-tracking difficult, unless you have a specific goal in mind that you can measure progress along the way on.