decrease to a fifth

Hi everyone, I'm having some problem with this sentence:
Petrol, on the other hand, was the only source of energy which decreased in production from 29.27% in 1995 to around a fifth (19.55%) in 2005.
I saw it on the internet and I'm wondering what decrease to a fifth means.
I think if it decreases from 5 to 1 then it decreases to a fifth. If it decreases from 5 to 4 then it decreases by a fifth. Am I right?

19,55% is a fifth of 100% (of the energy production).

Hi everyone, I'm having some problem with this sentence:

joseph1199 said:

Petrol, on the other hand, was the only source of energy which decreased in production from 29.27% in 1995 to around a fifth (19.55%) in 2005.
I saw it on the internet and I'm wondering what decrease to a fifth means.
I think if it decreases from 5 to 1 then it decreases to a fifth. If it decreases from 5 to 4 then it decreases by a fifth. Am I right?

Click to expand...

I find the original puzzling too.
AutumnOwl has identified what it means but I wonder why the author introduced a fraction into a list of percentages. It’s complicating rather than clarifying.

In my view they should have left it out OR ADDED “nearly a third (29.7%)” to make the two parallel.