This feels like a mixed blessing. Gamblers look for fast feedback on their investment, so their interest in the market likely adds short-term volatility. For

This feels like a mixed blessing. Gamblers look for fast feedback on their investment, so their interest in the market likely adds short-term volatility. For people investing for investing purposes (as opposed to gambling) the gambler's activities appear as "noise in the signal" and might make investing more challenging. On the other hand, a $2 drop in market investment for every $1 in sports betting could cause large changes in both investment strategy and in central bank behavior. In the US at least, the "economy" and the "market" are the felt to be the same thing, so any drop in the market could be interpreted as an economic slow-down. If that linkage holds, then the central bank might lower interest rates or otherwise "increase liquidity" and CEOs might call for more stock buy-backs to keep the valuations high.