Table 4. Supply-side factors associated with informal payments.

Supply-side factors	Number of citations	Study reference
Healthcare worker characteristics
Age	2	46, 49
Cadre	7	32, 33, 38, 42, 45, 49, 50
Health facility manager/in-charge/head of department	2	47, 49
Consultation venue i.e. health facility/healthcare workers residence	1	43
Salary (amount and timeliness)	8	32– 34, 37, 40, 45, 49, 50
Absence of allowances e.g. transport, risk	1	45
Health facility characteristics
Level of facility	5	34– 36, 47, 48
Facility ownership (public/private for profit/private non-profit)	4	34, 37, 39, 42
Facility location (rural/urban)	2	47, 48
Waiting times	3	31, 37, 48
Task shifting	1	37
Poor working conditions	1	45
Number of healthcare workers	2	45, 46
Lack of/stock out of essential drugs	2	13, 48
Presence/absence of official charging policies	3	39, 43, 50
Accountability mechanisms for user fees	1	46
Supervision/oversight over health worker behavior	2	33, 49
Poor health facility management	1	41
Engagement in informal charging/corruption by senior staff/facility managers	2	34, 45
Action against corrupt practices	1	32
System-level characteristics
Corruption among top health sector management	1	45
Wide-spread corruption in the public sector	2	40, 45
Health worker post rotations	1	44