Below are graphs showing how many poems, stories and Flash pieces I've written and had published since 1991.
I was curious about whether writing lots of Flash suppressed my poetry or story writing. Though a peak in the production of one type of writing often coincides with a trough on another graph, it as often coincides with another peak, so although there's a relationship it's not a simple one. I guess Flash and stories are most nearly the inverse of each other, which isn't such a surprise.
If one views the blue lines (how much I wrote) as quantity and the red lines (how much I published) as quality, I'd say I've not improved over the years. Nor has my quality control changed - the more I write, the more I get published, though my volume of output (which is never high) is patchy to say the least. Some years I produce no examples of a mode. Stories in particular don't come naturally - I have to commit myself to writing them; the temptations of Flash/Microfiction are too great. Increasingly my stories are episodic, a sequence of related flashes.
Or perhaps earnings should be the measure of quality. I hope not, but for completeness, here's the data.