Mouseferatu
Hero
That does nothing to change the average strength of a world's halflings.
If you're the DM, it does. If you're not, the DM is going to give the halflings whatever average Strength makes sense to him/her regardless of whether the rules list a concrete penalty or not. Most NPCs without class levels (or otherwise built as monsters/combatants) have pretty mediocre stats anyway, and those that don't are supposed to be the exceptions, just like adventurer PCs.