An advance thanks to all of you for helping out!

I am trying to plot a continuous variable (Income) against cumulative percentages (of number of households) to study what % of households have a particular income level. A basic line graph does this well. And the result is a kind of S graph.

However, the next step is to compare this relationship for different geographical areas, SEC classes etc. So I chose a multiple line graph, but since the size for each province would be different, on the y-axis they end at different levels (at the % of total population relevant to them).

Problem: how can Province A and Province B shown on the same graph if y-axis has cumulative percentages?

I hope I have been able to define my problem accurately. Please ask if you may have a solution but I haven't been clear enough!

Thank you!