Table 2.

Concordance rate of monozygotic and dizygotic twins in the indicated countries

Study population	Relation	No. of twin pairs	No. of concordant pairs	Probandwise concordance rate (%)
Australia[95]	Monozygotic	14	6	61
	Dizygotic	32	2	12
Finland[28]	Monozygotic	44	12	42.90
	Dizygotic	183	7	7.40
Japan[96]	Monozygotic	19	7	53.81
	Dizygotic	13	1	14.31
United States[25]	Monozygotic	53	12	36.91
	Dizygotic	30	0	0
Denmark[97]	Monozygotic	26	10	53
	Dizygotic	69	4	11
Finland[98]	Monozygotic	26	3	23.10
	Dizygotic	83	2	4.80
North America[27]	Monozygotic	132	38	45
	Dizygotic	92	13	25
United Kingdom[99]	Monozygotic	49	15	25 (1 yr)1
				40 (5 yr)1
				50.7 (10 yr)1

¹Rate not listed in original study, but calculated here based on the equation (2C/2C+D), where C is the number of concordant twin pairs and D is the number of discordant twin pairs.