The Team Shooting Percentage statistic measures the percentage of a teams shots on net that are goals. It's calculated by simply taking a teams overall goals and dividing it by the number of shots on goal the team generates over the same period.
More about Team Shooting Percentage
League wide shooting percentage has changed over the seasons due to evolution in the game, which has become more defensively focused and led to lower overall scoring and thus lower shooting percentages. However, since the 2009-10 NHL season, the average team shooting percentage has been steady around the 9% level.
To get more information on team shooting percentages, read: What is the average shooting percentage in the NHL?