The article explores how costs in businesses can behave differently when sales go up compared to when they go down. This difference in cost behavior is called 'cost stickiness'. The researchers used a special method called quantile regression to study this phenomenon and found that cost stickiness is not the same for all levels of sales changes. They also discovered that during a crisis, the relationship between costs and sales changes can change. This research shows that costs in businesses can be sticky, meaning they don't always decrease as much as they increase when sales change.