Table 1. Characteristics of Included Studies.

Authors	Country	Participants and setting	Type of donor	Groups
				Control group	Incentive group
Ferrari et al. (1985)	US	Posters and bulletins posted around a US University campus with announcement about time and place of blood donation	Both first-time and previous donors	n = 31Peer altruism. Students were informed that their peers would be donating blood	n = 49Offer of coupons redeemable at local merchants for free or reduced-price merchandise and a raffle (tickets to Broadway play, college football game)
Reich et al. (2006)	US	Blood Centers in San Francisco and Arizona; Outcome second and third donations of first-time donors within 6 months	Previous donors	n = 3,441	n = 3,478Offer of a t-shirt
Mellström & Johannesson (2008)	Sweden	Regional Blood Centre Gothenburg Sweden; Primary outcome health check for blood donation	First-time donors	n = 89	n = 85 Offer of $7 n = 88 Choice between $7 and donation to charity
Goette & Stutzer (2008)	Switzerland	Zurich Blood Donation Service of the Swiss Red Cross; individuals registered in the database invited to donate blood again	Previous donors	n = 2,950	n = 4,431 Offer of a free cholesterol test n = 1205 Offer of a lottery ticket from Swiss State Lottery
Goette et al. (2009) Study 1	Switzerland	Zurich Blood Donation Service of the Swiss Red Cross	First-time donors	n = 725	n = 1,400 Offer of a free cholesterol test
Goette et al. (2009) Study 2	Switzerland	Zurich Blood Donation Service of the Swiss Red Cross 8269 previous donors	Previous donors	n = 1,968	n = 3,812 Offer of a free cholesterol test
Lacetera et al. (2012)	US	The American Red Cross (ARC) conducted 14,029 blood drives in US northern Ohio between May 2006 and October 2008	Previous donors	$5 n = 10,846 $10 n = 12,515 $15 n = 12,607 Total n = 35,968	$5 n = 17,847 $10 n = 15,849 $15 n = 12,738 Total n = 46,434 The different amounts refer to gift cards redeemable for food, gasoline and general merchandise.