How do I improve the "economic base compared to" value?

I'm confused by the "you economic base compared to XXX" modifier when trying to vassalize a nation. I am frequently a very large nation trying to vassalize a relatively small nation and the only thing stopping me is this modifier. Moreover, this modifier is frequently -60 or more. From the wiki I saw that the minimum value of this modifier is -90, so I'm confused at how such a large nation can have such a lot economic base.

What do I need to do to improve this value?

Solution 1:

This modifier is quite difficult to overcome. It is calculated as a ratio of your economy to the target's, raised to some power, larger than 1. So it grows very fast and non-linearly. Easiest way is to conquer lots of land somewhere else or make your target lose some territory. Making target smaller is more efficient, because the ratio drops much more quickly (remember the power in the equation). Just make sure not to take target's cores - having target's cores gives -1000 modifier.

Solution 2:

It's quite simple, really. The formula works as follows:

90 * ((your base tax and production) / (your target development)^2) - 60

I don't like this system, it makes countries a fiftenth of your size impossible to peacefully vasalize if they have more than 20 development, I wish they changed that.