Adjusting for Era

Comparing over a century of hockey statistics is an ambitious task. The variables to consider in order to fairly compare eras can seem limitless at first. Fortunately for us, the groundwork has already been done. The foundational concepts of adjusted statistics in hockey are creations of Hockey-Reference.com – a cog in the vast encyclopedia of the Sports Reference online database.

Sports Reference, a comprehensive online historical database of seasons, teams, players, leaderboards, awards, and beyond, hit the Internet in 2000.  It was founded as a baseball statistical website out of the revolutionary mind of Sean Forman, then a 28-year-old working Ph.D. student. The group of sites has since expanded to other sports. Sports Reference’s network includes football and basketball (both at the professional and college levels), soccer, and most critical to our project, hockey.

Despite the volume of the data needed to get there, the underlying concepts of Hockey Reference’s adjusted statistics are more straightforward than you might expect. Simply put, a player’s counting stats are adjusted to fit a modern NHL season. In over a century of NHL hockey, there have been rule changes, scoring booms and busts, evolution in the distribution of assists, schedule length fluctuations, lockout and COVID-shortened seasons, and the gradual expansion of rosters. Bring the statistical results of each season in line with today’s environment. That’s what’s needed to level the playing field.

A single webpage on Hockey Reference’s website lays out the premise. The page and the corresponding outputs, in my view, have waited patiently for someone to shine light on its immense historical value. Like the players that these adjustments assign proper credit to, my Adjusted Hockey project seeks to give proper credit to these brilliant resources – while taking them further.

So, what does a modern NHL season look like?

ADJUSTED NHL SEASON vs. 2018-19 NHL SEASON

Environmental Factor	Adjusted	2018-19
Total Goals per Game	6.00	5.96
Total Assists per Game	10.00	10.06
Regular Season Games per Team	82	82
Number of Skaters per Team	18	18

A neutral season, in an adjusted world, is a regular season with six total goals scored per game, 1.67 assists awarded per goal (i.e., 10 assists per game), an 82-game schedule, featuring teams dressing an 18-skater roster. This adjusted season framework closely represents modern NHL norms; using 2018-19, the last full NHL season before COVID-19 for comparison, we can see how closely an adjusted season compares to the NHL of today. The adjustments do not require controversial leaps to integrate. The inputs are taken from the NHL’s official record, plus some research into historical roster sizes by year before they were standardized in the early 1980s. From there, the adjustments effectively bring those inputs to the NHL environment we enjoy today.

To properly contextualize players and seasons, an understanding of how the NHL has changed over its 100+ seasons is important. If we want to compare the 44 goals that “Phantom” Joe Malone scored in the inaugural 1917-18 season to the 41 goals that Auston Matthews scored in the pandemic-shortened 2020-21 season, we need to understand the colossal changes that have shaped the NHL’s basic counting numbers that comprise its statistical record.

Before we dive into the adjustments, we’ll spotlight a famous hockey father and son, identifying what timing and environment can reveal about their scoring totals and legacies.

Data from Hockey-Reference.com.