Complex sentence: Between 1832 and 1989, numerous Acts of Parliament increased the number of people from 5% of the adult population to the system of universal suffrage for all people 18 or over that exists today.
Split into simpler sentences: Between 1832 and 1989, numerous Acts of Parliament increased the number of people allowed to vote. The expansion was from 5% of the adult population to the system of universal suffrage for all people 18 or over that exists today.