A variable factor of production is one whose usage rate can be changed easily.

The centre has had a very promising first year with good uptake and usage rates.

That's dramatically below usage rates in other developed countries.

The nation's usage rate has risen considerably over the past couple of decades, to nearly 80 percent today.

Western countries have among the highest usage rates per person.

The usage rates for these services are low, and that may signal a large untapped market.

The recommended usage rate is 500 mg per serving by the company.

(There was no change in usage rates among people over 26.)

Despite this, the national usage rate climbed from 15% to 50%.

And the lower usage rates aren't due to some "farmers don't need the Internet" attitude.