Varying degrees of IGE

[dzeroplus]

From the wealth of knowledge out there, I was wondering if somebody could assist me answering a question I received from a student.

We are told that IGE occurs when the helicopter is one blade span above the ground (with minimal wind, not on sloping ground, not over water or grass).

Does the helicopter achieve greater IGE by being only 6 inches above the ground as compared to being 5 feet above the ground, as compared to being 15 feet above the ground?

Or is Ground Effect just standard (same value) anywhere between 6 inches and 15 feet (R22).

Thanks in anticipation!