Yes, unless you have a secret way of ruling out the other much more likely factors (i.e what GP mentioned).
You could argue that those countries still use leaded gasoline because the political turmoil/violence within them makes folks prefer the cheaper, easier fuel to produce.
Is it cheaper or easier to produce? The industrial process is difficult and hazardous. An alternative anti-knock agent is ethanol, which you can make at home. Originally, leaded gasoline was pushed by GM because they held the patents.
Ethanol production competes with citizens for food (how many of those countries using leaded gas have experienced famines recently?). Adding it to gasoline results in a fuel with ~30% less energy per unit, so you'd have to produce more gasoline to get an equivalent amount of energy.
I've read a study (can't find the link, sorry) comparing the cost of various ways of boosting the octane rating. Of all the alternatives (TEL, aromatics, alcohols, ethers, MMT, etc.) TEL was the cheapest.
I wonder what fraction of TEL consumption worldwide is due to aviation vs. these few remaining countries that use it in motor gasoline?
Yes, unless you have a secret way of ruling out the other much more likely factors (i.e what GP mentioned).
You could argue that those countries still use leaded gasoline because the political turmoil/violence within them makes folks prefer the cheaper, easier fuel to produce.