One reason why researchers have not fitted higher-order Markov models more frequently may be that researchers may not be aware that it is possible to fit such models using readily-available software. Second, higher-order models require long runs of panel data and these data may not always be available. One might argue that first-order DREP models are sufficient to capture the key distinction between heterogeneity and state dependence as determinants of SA receipt histories - note e.g. the relative unimportance of second- and third-order lags cited earlier - but the veracity of this case has not been rigorously scrutinised. An additional complication arises from the fact that approaches for dealing with the initial conditions problem need to be adjusted when higher-order lags are added to the DREP model.