How much is loot reduced for raiding lower Town Halls?

I am thinking of upgrading my Town Hall to level 10. I am bored of upgrading my walls. In info while upgrading my Town Hall it says upgrading Town Hall would provide less loot from lower Town Halls, but how much less loot?. If the effect of loot reduction after upgrading my Town Hall is less then I would upgrade my Town Hall. Does anybody know how much loot is reduced for lower Town Halls?

I found a page on www.clashofclans.wikia.com that states

Town Hall Difference - Percentage of Loot Available

Same or higher Level - 100%

1 level lower - 80%

2 levels lower - 50%

3 levels lower - 25%

The difference is your TH level vs their TH level, so if your TH is higher you get a penalty.