Strength state
also: 5v5 · even strength · manpower situation
How many skaters each side has on the ice. Almost every number worth reading is filtered to one of these.
Every play carries the skaters on each side at the moment it happened: 5v5, 5v4, 4v5, 4v4, 3v3, and the empty-net variants. Possession and expected-goal figures here are computed at 5v5, which is where roughly three quarters of a game is played and where teams are compared on equal terms.
Mixing states ruins a comparison. A team that draws a lot of penalties will out-attempt the league across all situations without being better at hockey; a team that takes them will look worse than it is. Filtering to 5v5 removes both effects, and special teams get measured on their own.
The play rows expose the state directly, so you can rebuild any of this at 5v4 or 4v4 instead. That is the main reason the field is returned rather than folded away into a pre-filtered aggregate.
Reading an all-situations number as if it were 5v5. If a source does not say which state it used, it is usually all situations, and it is usually not comparable to anything here.
Where to get it
Related
Strength state from the API
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