There's a nasty interaction among those concerns: as the basic staple food of the diet, rice is consumed in larger amounts by poorer people who can't afford real food, like meat.
Which means that a spike in the price of rice is effectively targeted at people who can't afford to substitute other foods.
I understand most cultures over-appreciate meat, but treating a premium carb source like rice lowly is a surprise.
I can't personally attest to that, but it certainly makes sense. Rice meals vs noodle meals are a fairly fundamental split in Chinese cuisine.
(It doesn't make rice any less of a staple food.)
I find this an interesting contrast with the United States, where the default cooking oil is Canola oil (if you're a person looking to cook your own food; this is the sense in which the Chinese default is corn oil) or soybean oil (if you're a company looking to sell packaged food in grocery stores). As far as I'm aware, traditional China would have had sesame oil and maybe soybean oil, and certainly not corn oil. The advantage of corn oil must be the price.
But if corn oil is so cheap, why does the cheapest oil available in the US seem to be soybean oil?
China also imports 80% of its soybeans which means it's based on the rising/falling prices of oil and whatnot.
In the US, soybeans are a very important crop that's fed to livestock and also used in biodiesel production. There's enormous soybean "crush" infrastructure in the US to support the biodiesel market and the side effect of this results in tons of extra soybean oil. It ultimately ends up with soybean oil being cheap compared to everything else.
Um, rice is real food too, right?