How to create body where the bottom is scaled vs. the top ? (with picture)

[ittay.dror]

Basically, I want to create something along the lines of the following image:

The top is scaled down vs. the bottom in one axis. (I did the above in Sketchup by pulling the base and then moving the point at the top)

[etfrench]

Use dimensions and user parameters.  You can enter formulas which relate the sizes in either of these.

[jeff_strater · Accepted solution]

I would do this as a loft, with two sketches.  You can use parameters, as @etfrench suggests, for precise control

Jeff