Imagine a household of three.
Imagine a household of three 20-something year olds sharing a flat.
Imagine the flat has three rooms, a big one, a small one, and a mid-sized one. (The big one has also the nicest view.)
Imagine the three 20-something year olds work:
Peter is a software developer and works full-time. He makes the most money of the three.
Paddy is a part-time call-center clerk and works 20 hours a week. He makes less money per hour than Peter.
Paul is an office drone of some kind and works full-time. He makes as much per hour as Paddy.
Imagine that Peter lives in the big room, Paddy in the small room, and Paul in the mid-sized room. Peter has also bought a TV for the living room (which all three use), a super expensive computer for his room, and a washing machine for the household (it's in the kitchen). Paul bought himself a less expensive computer for his room. Paddy cannot afford a computer and spends most of his time, including the time the others are at work, watching TV in the living room.
Imagine that, for some reason, a politican from another street decides how much of the rent they each must pay.
What would the politician decide?
If he was a modern liberal he would decide that each of the three will pay rent according to how much they make. This results in Peter paying 80% of the rent and Paul paying 20%. Paddy pays nothing.
If he was a classic liberal he would decide that each of three will pay rent according to their room size, independent of their income and other holdings. This results in Peter paying 50% of the rent, Paul paying 30%, and Paddy paying 20%.
If he was a conservative he would decide that each of the three will pay rent according to the value of their rooms including property in it. This results in Peter paying 60%, Paul paying 35%, and Paddy paying 5%.
If he was a socialist he would decide that Peter, Paul, and Paddy should make the same amount of money. He thus decides that Peter and Paul will henceforth pay a part of their income into a fund from which Paul and Paddy can withdraw money. This involves lots of forms and hearings. Afterwards, all three are paying the same share of the rent.
If he was a communist he would decide that Peter and Paul will only be allowed to make as much money as Paddy and that all three should pay the same amount of rent. Also, the two bigger rooms will be made smaller. This results in Paul working only 20 hours a week from now on and Peter working only 10 hours a week now. The policitian does not understand why the three of them together seem to have less money than before.
If he was an environmentalist he would decide that each will pay according to their negative influence on the flat. For example, Paul uses the bathroom longer in the mornings and Paddy has the most cloths to wash. Peter is very much in favour of this. But it results in Peter paying 90% because he has the most money, Paul paying 30% because of the bathroom issue, and Paddy paying 10% because he is poor. It is not clear to any of them why they suddenly pay more in total.
If he was a progressive centrist he would try to determine how much each should pay according to their respective incomes, room size, personal property, needs, and wants. The exact percentages would change every month depending on individual input. It involves A LOT of forms and hearings and living room meetings. The majority of tenants agree that it is fair. Peter usually pays around 80% of the rent.
If you were the politician, what would you decide?