Why are there such wide discrepancies between MPI poverty estimates and $1.90 per day poverty estimates in so many countries?

The MPI complements income poverty measures. It measures various deprivations directly. In practice, although there is a clear overall relationship between the MPI and the $1.90 per day measure, the estimates do differ for many countries. This is a topic for further research, but some factors can include the provision of public services, as well as different abilities to convert income into positive outcomes such as good nutrition.