[Quantlib-users] Year-on-year index not defined as ratio?

[Luigi B. <lui...@gm...>]

Hello everybody,
    in the `YoYInflationIndex` class, we have a `ratio` parameter that
tells us whether or not the index is the actual year-on-year ratio of an
underlying CPI index.  I see the `ratio=true` case as the "usual" case, but
I don't really see how the `ratio=false` case would work—do indexes exist
which are published as a supposedly year-to-year index, but are independent
of an underlying index? And in that case, what does year-on-year even mean?

Do you have any examples?

Thanks,
    Luigi