The following four charts contain U.S. Department of Agriculture (USDA) information that provide perspective on U.S. commodity corn exports, uses, and price. This information can correct widely circulated, inaccurate information on these topics.
This USDA chart gives you the longer-term view over the past five decades. The red layer shows that China has been a major exporter of corn since the 1960's.
This USDA chart shows there were really only a few points in the past half century when there was even a blip of import activity from China (see purple peaks on the top layer).
Look at the facts about China's corn imports from the U.S.
See the first bar on the left for each year. The tiny red column shows exports of U.S. corn to China. That's about 1% of the U.S. crop over the past few years.
Even the next bar, the blue one, shows total U.S. corn exports are not the major use - just about 15% each year. By far, most U.S. corn is used domestically.
This USDA Economic Research Service statement reinforces the data.
“Although the United States dominates world corn trade, exports account for a relatively small portion of demand for U.S. corn--about 15 percent. This low demand for exports means that corn prices are largely determined by supply-and-demand relationships in the U.S. market, and the rest of the world must adjust to prevailing U.S. prices.”
“China has been a significant source of uncertainty in world corn trade, swinging from being the second-largest exporter in some years to occasionally importing significant quantities.”
Source: USDA ERS
You can see in this USDA chart of commodity corn price data, that the major price decline occurred between July and October 2013. This was prior to China's rejection of U.S. corn in November 2013.
Also, see the corn stocks data below each year. From 2013, corn stocks continued to rise significantly from 8 billion bushels to more than 11 billion in 2015. As key observers have noted, including USDA, commodity corn price is based on supply & demand in the U.S.