Of course there is a large drop in production between the 2nd and 3rd/4th lines almost every season. This season there was no drop between the 1st and 2nd lines, so the drop between the 2nd and 3rd lines was larger than normal. What did hurt this season was the lack of goals from the 3rd and 4th lines as their combined 19 goals was tied for second lowest in the past ten seasons. The 19 goals also accounted for just 19.6% of all goals from the forwards, third lowest in the past ten seasons (barely beating out 2014-15's 3rd/4th lines 19.4%).
I added forward line combinations and defensive pairing to my database a number of years ago. My information is based on depth charts and/or lineups listed in online game boxes. I know some of those conflict regarding line order and I try to be consistent and use the depth charts, then the online boxes. Also powerplays, penalty kills, injuries, games misconducts and in game changes can all affect line scoring, so my stats will not be 100% accurate. Still, I believe them to be quite useful in comparing lines and defensive pairing. As I was asked about the stats for this season's third line I ran queries for stats by forward line and defensive pairing for the past ten seasons. I created a
spreadsheet and uploaded it if anyone else is interested. I also added the averages and medians for all ten seasons so each season can be compared to them.
Sean