Table 2. Frequency of sibling aggression by age.

	Age 7-10		Age 11-14		Age 15-18
	Child report	Mother report	Child report	Mother report	Child report	Mother report
Prevalence of any mild sibling aggression	80%	94%	81%	97%	84%	88%
Prevalence of any severe sibling aggression	52%	77%	59%	75%	53%	56%
Mean mild sibling aggression (standard deviation)	8.96 (9.59)	19.48 (10.07)	12.34 (10.63)	20.53 (10.84)	14.27 (10.71)	17.04 (11.11)
Mean severe sibling aggression (standard deviation)	4.20 (7.74)	9.50 (10.04)	5.87 (9.32)	9.18 (10.16)	4.70 (7.62)	5.67 (8.40)