Water

Consider the molecules in a glass of water.

Randomly, some will diffuse upward, some downward. But this mobility is not equal; a molecule that reaches the top may escape into a more rarified state, escape the surly bonds of hydrogen bonding and be one with the upper air. Indeed, what holds most molecules of water back is other molecules of water.

Now consider this statement.

"The progress of the lowest 90% of the population is far lower than that of the highest 1% of the population."

There is nothing new under the sun. How can it be otherwise?

Well, yes, there are alternatives. If your glass of water is a glass of steam, then most of the molecules are in random motion and will soon escape the glass. Some will hit a glass wall and condense, having lost sufficient energy or been sufficiently attracted to the glass or other molecules of water. If your glass of water is a glass of ice, nobody goes anywhere.

But a glass of water is normally taken to be just that — a glass, with liquid water in it.