3. Type of electronic search strategy used.

No. studies	Comparison	Type of search	Median no. trials	HS retrieval	ES retrieval	% Difference
9 studies	HS versus ES	Simple	385 (IQR 86‐729)	0.98 (95% CI 0.97‐0.98)	0.42 (95% CI 0.41‐0.43)	56%
30 studies	HS versus ES	Complex or Cochrane HSSS	198 (IQR 39‐344)	0.94 (95% CI 0.93‐0.95)	0.65 (95% CI 0.64‐0.66)	29%
14 studies	HS versus ES	Cochrane HSSS	193 (IQR 30‐483)	0.93 (95% CI 0.93‐0.94)	0.80 (95% CI 0.79‐0.82)	13%
12 studies	HS versus MEDLINE	Cochrane HSSS	193 (IQR 43‐442)	0.93 (95% CI 0.93‐0.94)	0.73 (95% CI 0.71‐0.74)	21%