The study looked at how the density of Norway spruce and Scots pine forests in Norway affects their growth. They used data from national forest inventories to analyze this relationship. The results showed that both tree species grow more in denser forests, but the growth slows down at very high densities. Thinned forests grew about 10% more than unthinned ones. The study also found that volume growth decreases more in less dense forests than previously thought. Overall, the research showed that forest inventory data can be useful for studying how tree density affects growth.