the claim that, other things being equal, the quantity supplied of a good increases when the price of that good rises

The statement “the claim that, other things being equal, the quantity supplied of a good increases when the price of that good rises” is simply the standard definition of the law of supply in economics.

What that claim is saying

Put in plain language, it means:

• When the price of a good goes up, producers are willing to sell more of it.
• When the price goes down, producers are willing to sell less of it.
• This is stated “other things being equal” (ceteris paribus), meaning:
  • Technology, input prices, number of sellers, government policy, and expectations are all assumed constant.

Because of this positive relationship between price and quantity supplied, the supply curve is drawn as upward‑sloping in a standard price–quantity graph.

Why quantity supplied rises with price

Economists usually give two main reasons.

1. Profit incentive
   • A higher price means higher revenue per unit sold.
   • If price rises while costs per unit are unchanged, producing and selling more becomes more profitable.
   • New firms may enter the market because they now see a chance to earn profit at the higher price.

2. Rising opportunity cost
   • As a firm expands output, it has to use resources that could produce other goods.
   • The more it shifts resources into this good, the more it gives up producing alternatives, so the opportunity cost of additional units rises.
   • A higher price is needed to compensate the firm for this higher opportunity cost, so only at higher prices will firms supply larger quantities.

Example: If the price of wheat doubles, farmers may plant more land with wheat instead of corn because the higher wheat price better compensates them for giving up corn production.

“Other things being equal”: why the caveat matters

That phrase is crucial because the law of supply describes a movement along a given supply curve, not a shift of the curve itself.

• A change in price alone → movement along the supply curve (higher price, higher quantity supplied).
• A change in other factors (input costs, technology, taxes, number of firms) → shifts the entire supply curve:
  • Better technology or lower input costs makes supplying easier at every price → supply curve shifts right.
  • Higher input costs or new taxes make supplying harder → supply curve shifts left.

So the claim is conditional: holding all non‑price determinants constant, price and quantity supplied move together in the same direction.

Is the law of supply always true?

In standard introductory microeconomics, the law of supply is treated as a general rule and is embedded in the usual model of competitive markets. However, economists recognize important nuances:

• For some mass‑produced goods , unit production costs fall as output expands (economies of scale), which can complicate the simple upward‑sloping story.

• Some heterodox economists argue that in certain industries the effective supply curve may even slope downward over relevant ranges, because average costs fall as output grows and firms set prices based on markups over cost.

• In the very short run , capacity constraints can make quantity supplied almost fixed regardless of price.

Even so, as a simplified, broad principle for competitive markets , the law of supply remains a foundational idea: higher price → higher quantity supplied, ceteris paribus.

TL;DR:
“The claim that, other things being equal, the quantity supplied of a good increases when the price of that good rises” is the textbook statement of the law of supply: it describes a positive, ceteris‑paribus relationship between a good’s price and the amount producers are willing to bring to market.

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