Just 55 percent of the world's crop calories are actually eaten directly by people
"We find that on a global basis,crops grown for direct human consumption represent 67%of global crop production (by mass), 55% of global calorieproduction, and 40% of global plant protein production(table 2)"
Redefining agricultural yields: from tonnes to people nourished per hectare, p. 3By Emily S Cassidy, Paul C West, James S Gerber and Jonathan A Foleyhttp://iopscience.iop.org/1748-9326/8/3/034015/pdf/1748-9326_8_3_034015.pdf