Belgian firms were surveyed in 2004 to study how they set prices. The results showed that firms have some power in the market and often adjust prices based on what competitors are doing. Prices tend to stay the same for about 10 months before being reviewed, and 13 months before actually changing. This suggests that it can be costly for firms to change prices. Most firms stick to a set schedule for reviewing prices, but may change this if something unusual happens. The survey also found evidence that firms don't always set prices optimally, which could be due to not having all the information they need.