Credit-fuelled bubbles happen when people borrow money to buy things like houses or stocks, causing prices to go up. This makes lenders give out more money, which makes prices go even higher. Some people know the prices are too high but still buy hoping to sell to someone else for more money. Eventually, prices crash, and people who bought at the peak lose money and their collateral. The study shows that making borrowing harder can stop or reduce these bubbles, which is what most experts already believe.