Rate constants for substitution of inner sphere water molecules on metal ions

I like trends, I like rules, I like to explain things using them. The moment I saw this table of rate constants, I fell in love with it. The study was done by Manfred Eigen and his colleagues and I think it is brilliant. Here is the table and the paper :  

The main trend is obvious. In the same group, the rate of exchange increases with the size of the ion.

There are also other very important trends  and exceptions that he lists in the paper in case you are interested. The great thing is that they can be explained by certain rules that you learn in undergraduate inorganic chemistry courses. I love it!