From 1961 to 2011, while the population of UP went up to 19,98,12,341, almost three times of what it had in 1961, Kerala saw a balanced increase almost the same number that it had in 1961, to 3,34,06,061.
The why of it and the results of it reflect in various socioeconomic indicators of the two states.
While the literacy of Kerala went up to 94% from 48% in 1961, touching even 100% in pockets, UP is still way behind, from almost 15% in 1961 to 68% now. The huge population difference between Kerala and UP make this gap even more telling. Then quality of literacy is also a big issue here, reflecting in indicators like poverty and mortality rates.
In 1961, Kerala's infant mortality rate (per 1000 live births) was 52 that has come down to 10 now. UP's IMR in 1961 was 130 and is still 64. So, Kerala cut it to five times while UP could only halve it in the same period. And if we see, the gap between Kerala and UP has gone up. UP's IMR in 1961 was 2.5 times of Kerala's. In 2011, it is 6.5 times.
These are some of the pointers based on the historical comparison with the data set available. Even if we compare both the states on present day parameters, we find Kerala comfortable positioned than UP.
With majority of the Indian population living below the poverty line if we take the global benchmark of $1.9 a day, poverty is the most important indicator to assess the social and economical well being of both of the states.
Going by the findings of the Tendulkar Methodology to determine and define poverty in India, Kerala had its 7.1% population living below the poverty line in 2011-12 while the corresponding figure for UP stood at 29.4%.
It means Kerala has just 23.40 lakh people living below the poverty line while UP is yet to uplift its 5.55 crore from the chasm of poverty and mind you, these figures are based on abysmally low Indian poverty line, Rs 27 in rural areas and Rs 32 in urban areas (by Tendulkar panel's recommendations).
PS: I am a UP walla, a proud Banarasi.