Now, the equation for yield is the following. So it's the ratio of the enzyme activity of that specific procedure to the original enzyme activity found in that original sample that we begin with and we multiply the ratio by 100%. So because this is a ratio, the units cancel out and our units are simply percent. Now, by definition we give our original sample that hasn't yet been purified a yield of 100%. And then as we purify our sample more and more the yield should technically decrease. Now, what about the purification level?