Video: Benefit system can have an impact on number of births Iain Duncan Smith at a speech at Cambridge Public Policy, a think tank associated with the university, will say the current payment of benefits is supporting "dysfunctional behaviour" and that for some families "the notion of taking a job is a mug's game." Mr Duncan Smith will say: "You have to ask which bits of the system are most important in changing lives. And you have to look at which parts of the system promote positive behaviours and which are actually promoting destructive ones. Social Market Foundation director Mr Mulheirn agreed said benefit system can lead to increase in the number of births due to enabling working families to have children they would not otherwise be able to rather than out of work families having children they cannot afford. He said there was a limit to what Mr Duncan Smith to make work pay without extra funds beyond cutting welfare.