After Terri Nelson noticed people complaining online about a lack of scent from newly purchased scented candles, Kate Petrova analyzed Amazon reviews for candles from the past three years and found a drop in ratings for scented candles beginning in January 2020 (compared to a smaller ratings decline for unscented candles).
The hypothesis is that some of these buyers have lost their sense of smell due to Covid-19 infections and that's showing up in the ratings.