3. Interventions and comparisons in included studies.

Comparison 1: P4P plus an existing payment method compared withan existing payment method
Study	Intervention	Comparison
Christensen 2000	P4P + existing payment method	Capitation
Chung 2010	P4P + existing payment method	Not described
Fairbrother 1999	P4P + existing payment method	FFS
Fairbrother 2001	P4P + existing payment method	FFS
Gleeson 2017	P4P + existing payment method	FFS
Greene 2013	P4P + existing payment method	FFS
Houle 2016	P4P + existing payment method	FFS
Kouides 1998	P4P + existing payment method	FFS
Lee 2010	P4P + existing payment method	FFS
Li 2013	P4P + existing payment method	FFS
Petersen 2013	P4P + existing payment method	Not described
Singh 2015	P4P + existing payment method	Salary
Young 2007	P4P + existing payment method	Salary
Young 2012	P4P + existing payment method	Salary
Comparison 2: FFS compared withexisting payment methods
Study	Intervention	Comparison
Davidson 1992	FFS	Capitation
Lurie 1992	FFS	Capitation
Hickson 1987	FFS	Salary
Yesalis 1984	FFS	Capitation
Yesalis 1980	FFS	Capitation
Comparison 3: FFS mixed with existing payment methods compared withexisting payment methods
Study	Intervention	Comparison
Bilardi 2010	FFS + existing payment method	Not explicitly described
Clarkson 2008	FFS + capitation	Capitation
Twardella 2007	FFS + existing payment method	Not explicitly described
Jensen 2014	FFS + capitation	Capitation
Gosden 2003	FFS + salary	Salary
Gray 2015	FFS + capitation	FFS
Flierman 1992	FFS + capitation	Capitation
Krasnik 1990	FFS + capitation	Capitation
Comparison 4: Enhanced FFS compared with FFS
Study	Intervention	Comparison
Davidson 1992	Increase in FFS per service payment rate	FFS
Fairbrother 1999	Increase in FFS per service payment rate	FFS
Fairbrother 2001	Increase in FFS per service payment rate	FFS

FFS: fee‐for‐service
P4P: pay for performance