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, alcoho

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?