Table 1 reports the summary statistics for
several of the key determinants of mortality rates and provides
evidence on the validity of the RD design. Columns (1) and (2)
report the means in cities south and north of the Huai River line.
Column (3) reports the mean difference between the North and
the South. Column (4) also reports the difference, but this time it
is adjusted for a cubic polynomial in degrees north of the Huai
River so that it is a test for a discontinuous change at the Huai
River line. A direct test of the RD design’s identifying assumption
that unobservables change smoothly at the boundary is, of course,
impossible, but it would nevertheless be reassuring if observable
determinants change smoothly at the boundary. (This is analogous
to the test in randomized control trials that observable
determinants of the outcome are independent of treatment status.)
Column (5) reports the P values associated with the tests that
the differences in columns (3) and (4) are equal to zero.