Weekly agricultural prices often have predictable seasonal patterns, but it's important to check if these patterns stay the same over time. Regular tests might not always catch these changes, so a new method was developed to test for these patterns in weekly prices. When this method was applied to agricultural prices in Spain, it showed that some patterns that seemed to be there actually weren't, and vice versa. So, it's crucial to use both regular tests and this new method to understand how seasonal patterns in prices behave.