The newspaper is a product made fresh every day, but its feedback loop is quite slow. Meaning that it is not easy for the editor to tell what the sentiment or mood of the reader is. One objective way is through the sale of copies. A particular banner headline on Tuesday results in an increase over the number of copies sold on Monday.
That would indicate that the reader is more interested in the content of that Tuesday story. However, it is not so easy. The majority of newspaper sales is through subscription (home delivery) and so the sample size of retail sales is low. The other problem is that newspapers, especially broadsheets such as this one, are quite structured.