Grades are determined by curves. There's no absolute scoring in most university classes, especially in engineering and science programs.

Professors usually draw something similar to a bell curve along the grade distribution and set the average to be a particular grade. Grade inflation would be setting the average to something high (as practiced at Harvard this is usually an A-).

Grade deflation which both U Chicago and my alma mater Johns Hopkins are notorious for has professors set the average grade to a B-/C+. In classrooms full of students who have excelled their entire life, where the average represents a pretty high standard of work and achievement, setting the average to a B- is grade deflation.