The Bank of Nook cut the interest it pays on bell savings from .5% to .05%, or next to nothing. According to the Financial Times, the Bank of Nook was responding to a trick players discovered in which they could deposit a large sum of bells and then time travel into the future by adjusting their Switch's clock. From the Financial Times:
The total interest available on any amount of savings has now been capped at 9,999 bells — the in-game currency that can be bought online at a rate of about $1 per 1.9m bells.[…]
"Now that the [Bank of Nook] has cut interest rates to near zero, their next logical step is quantitative easing. It's essential that players try to hook their game up to their printers as it might start churning out money," [Albert Edwards, a strategist at Société Générale,] joked.
As many users pointed out online, the much lower interest rate means that the most effective way of making money is now to gamble on the game's internal "stalk" market — a bourse in which the only commodity is turnips, sold to investors during a single session on Sundays. The root vegetables rot and their value drops to zero after a week.