The per capita income of a country or a state within a country is not the sole criteria for development. Because the income of a person may not afford all the goods and services that he needs to live a good life.
To compare countries and states, we have to look at other variables like Infant mortality rate, literacy rate, sex ratio, maternal mortality rate, life expectancy etc.
For example, if we only consider per capita income for development, then while comparing Indian States Punjab, Kerala and Bihar, we see Punjab should be the most developed State out of them.
But if we look at other variables, the most developed State turns out to be Kerala instead.
The improvement of the qualities mentioned above depends on the role of the government in providing facilities to the people. These includes public facilities like healthcare, education, distribution of income and wealth schemes, controlling pollution and development of infrastructure etc. which help in welfare of people as a whole.
For example, Kerala has low infant mortality rate and high life expectancy because of its good healthcare system provided through government hospitals. Public distribution system(PDS) like rations also contribute in this regard.