However, randomisation does not necessarily drive the fact that only some individuals receive an intervention; they are particularly well-suited when for financial or logistical reasons the implementation and roll-out is slow or staggered, or when comparable groups are left out for other reasons. This is the reality of most development interventions. Part of what underlies the ethical concern about impact evaluations is the premise that assignment to a comparison or control group implies ‘not receiving a benefit’. This is not necessarily the case for two reasons. First, the comparison group can be receiving a treatment with which another competing intervention is being compared, as we saw in the multi-arm RCT. Second, it is important to examine the assumption that receiving a development intervention, or more of one, is always a benefit. The reality is that the effectiveness and impact of a large number of development interventions have yet to be proven.