child mortality rates are apples and oranges, every country calculates it differently.
That could be, but I don't worry about it. I try to use the CIA Factbook data which figured consistently. Really what you need to figure is the change in the rate, so how they calculate it is not relevant.
So, when a nation's fertility rate begins to fall, life spans increase(however they calculate it), child mortality rates fall(however they calculate it), healthcare levels increase(however they calculate it), incomes increase(however they calculate it), poverty decreases(however they calculate it), and education levels rise(however they calculate it)