It is both increased demand and shorter supply. In particular, the growing middle class in both India and China are eating more meat. Also add this to your list "Per-capita consumption of food in US is 5 times higher than in India and approx 4 times than in China". So, putting 20% corn into producing ethanol is tantamount to the total corn consumption of middle class in India. I guess the cause of global rising in food prices is more than clear.