I was never a fan of slowing the exp gain rate by messing with the bumpbase.
Those mods increase the amount of exp needed to gain a level by a multiplier. (1.2x, 1.3x, 1.4x and so on)
The problem with that is when you want to change one for another.
You can instantly gain a lot of exp, or take a long time to get to the next level.

So when Old World Blues came out, and had the Skilled trait, I figured there was a way to make a mod to do the same percent based exp reduction.
It took me a while to figure it out, but I finally got it working.
My mod DOES NOT change any exp values in the game. It just reduces ALL exp gains by a percent.

Each file gives you a perk that slows your exp gain by either -5, -10, -20, -30, -40, -50, -60, -70 percent.

So lets say you want to gain exp normal for 10 levels.
Then slow down exp for 11 to 20 by 20%.
Then slow down exp for 21 to 50 by 40%.

You would not use the mod for first 10 levels.
Then at level 11 drop the EXP -20%.esp in the data folder, and activate it.
Then at level 20 remove the EXP -20%.esp , and replace it with the EXP -40%.esp.

The reason I made many different values is that when put together they don't add together exactly.
You can use more than one at a time, but the game will not add them together.
The game will use each one separately.
So -20% and -40% will not equal -60%. The game will do -20% then do -40%
Example: a quest that gives 1000 exp will be reduced by 20% then by 40%.
So 1000 x .8 = 800. then 800 x .6 = 480. Using the single -60% would be 1000 x .4 = 400.

You can still use the mod with the OWB "Skilled" trait.
Just be aware that the above examples will happen.
So the reduction will not be exact.


Requirements...
(NVSE) New Vegas Script Extender
I am not 100% it is needed, but I have always been using it.
Considering it is a MUST HAVE for many mods. Go get it if you do not have it already.