The phrase "quantity has changed" is correct and can be used in written English.
You can use it to describe a situation where the amount of something has changed. For example, "We noticed that the quantity of eggs in the box has changed since we bought it."
What has changed is the quantity of business news, as investors choose among thousands of stocks and as corporations affect people around the globe.
But what has changed is the quantity and frequency.
The freight transport market has changed, from large quantities of bulk being transported by block trains, to smaller, more frequent shipments with a higher value and a faster and more reliable delivery requirement.
The Celtic Tiger has changed the quality, and quantity, of rubbish.
There is also widespread frustration at how little has changed, despite the huge quantities of money that have poured in here.
"Neither price nor quantity of credit extended in the euro area has changed much," Lucas D. Papademos, vice president of the central bank, said this month.
In America's eyes, China is more of an uncertain quantity than it was, while once-authoritarian Taiwan has changed into a flourishing democracy.
The whole business of comedy has changed — from 15 minutes of quality to quantity.
Quantity over quality is what begins to happen; the idea of what quality is has changed".
I certainly don't need the quantity of food I once did, but I don't believe the quality of food has changed much.
The drivers, either individually, or in combination, have changed the quantity, species composition, and spatial pattern of dispersed seeds in the majority of ecosystems worldwide, with inevitable consequences for species survival in a rapidly changing world.
