Table 1.

The match injury incidence (injuries per 1000 player-match-hours) of concussion in the first and last seasons of the injury surveillance period, and the proportionality constant from a weighted least squares fit of the incidences from all seasons

Data set	Incidence 2012–2013	Incidence 2015–2016	Weighted least squares proportionality constant
Club rugby	7.1 (4.3, 11.0)	21.4 (16.0, 28.0)	4.94 (1.69, 8.19)
International rugby	18.2 (5.0, 46.6)	22.2 (9.6, 43.8)	1.99 (−12.69, 16.67)
Combined club and international rugby	7.9 (5.1, 11.7)	21.5 (16.4, 27.6)	4.68 (0.81, 8.55)

Rows in bold indicate where the proportionality constant significantly differs from zero.