Do you want to know the number of downloads for each of your extensions on different marketplaces?
Actually, it is not impossible to track that. The idea is to create a script with cron which saves that amount and generates a graph everyday.
Write to console the status and generate a json for every extension specified in the config.ini (copy config-sample.ini and change depending on your needs), you can see a demo here.
bash:~/ExtStoreStats $ ./index.py
Addons Mozilla Extension Gathering for: glotdict
Download: 68
Google Web Store Extension Gathering for: glotdict/jfdkihdmokdigeobcmnjmgigcgckljgl
Download: 236
Total Download: 304
pip install -r requirements.txt