Which sequence converges fastest?

[onako]

I have the following sequences of numbers:
1) 32, 16, 8, 4, 2, 1
2) 32, 16, 8, 2, 1, 0.5
3) 32, 16, 4, 2, 1, 0.5,
4) 32, 16, 4, 1, 0.25, 0.0625

I'm interested which of the above has the fastest rate of convergence.
(mathematical formula is needed). I should be able to plot the rates of
convergence against each other, and it should be concluded from the plot.
(The data given above are just the illustration)

 

[onako]

This means I should be able to tell which sequence drops/decreases faster from the plot.
For example, given sequences {32, 16, 8, 4, 2, 1} and {128, 32, 8, 2, .5, .125} I should be able to tell that the second sequence drops faster (decreases by /4). How to extract this data and plot it, so that the answer is obvious? Thanks