Costco finds inflation is at zero; deflation looms.

[cally]

13. In economics, I learned deflation could be very bad

But I did some searches after reading the above thread. A few said it can be worse than inflation but it depends on why deflation is happening and how long it lasts. See linked article

I also found this encouraging from investopedia

KEY TAKEAWAYS
Deflation is when the general price levels in a country are falling—as opposed to inflation when prices rise.
Deflation can be caused by an increase in productivity, a decrease in overall demand, or a decrease in the volume of credit in the economy.
Most of the time, deflation is unambiguously a positive trend for the economy, but it can also under certain conditions occur along with a contraction in the economy.
In an economy dominated by debt-fueled asset price bubbles, deflation can lead to a temporary financial crisis and a period of liquidation of speculative investment known as debt deflation.
https://www.investopedia.com/articles/personal-finance/030915/why-deflation-bad-economy.asp