What is the theory of quantity and price

The volume price theory was first seen in "Stock Market Indicators" by Joe Granville, an American stock market analyst. Grumbi believes that trading volume is the vitality and motivation of the stock market. Changes in trading volume directly reflect whether the stock market is active or not, and it reflects the dynamics between supply and demand during the operation of the market. There is no occurrence of trading volume and market prices. It is impossible to change, and there is no stock price trend at all. The increase or shrinkage of the trading volume shows a certain stock price trend.