There is an unwritten rule in Switzerland that rent should not exceed one-third of income.

However, according to a new study conducted by the real estate company Wüest Partner, after a move to a new apartment, even a smaller one, a large portion of tenants are paying much more to cover the cost of new digs.

The study found that, on average, 28 percent of households spend more than a third of their income on rent after moving.

Why is that?

If you are looking for a new apartment and think that a smaller one will be cheaper, that is often not the case.

“A four-room apartment does not necessarily cost twice as much as a two-room apartment,” said Robert Weinert, head of immo-monitoring ar Wüest Partner Wüest Partner.

One reason is the persisting — and, in some cases, worsening — housing shortage.

Another is that when an old tenant moves out and a new one arrives, landlords have the right to increase the rent by up to 10 percent.

As a result, many older people, who find themselves alone after the children move out, live in large apartments they have had for many years.

For this very reason, the living space per person increases sharply from the age of 55 — these tenants live alone or with a spouse in their old apartments, which were previously occupied by three, four or five people, Wüest Partner said.

READ ALSO: Can you really save money on rent if you move into a smaller flat in Switzerland? 

Where do new tenants spend more than one-third of their income on rent?

Wüest Partner’s analysis found that this is especially the case in canton Geneva, where 56 percent of tenants see their rents exceed one-third of their earnings.

Zug is next with 40 percent, followed by Zurich and Vaud (36 percent), and Ticino (31 percent).

When looking at individual cities rather than cantons, this trend is most evident in the five largest cities — Basel, Bern, Geneva, Lausanne and Zurich —where a four-room apartment in an older building costs on average around 1,900 francs per month with existing rental agreements.

If an apartment of this type is put on the market today, however, the rent will rise to 2,300 francs on average.

Landlords must show you the previous rent upon request, so you can compare the numbers before you sign the contract.

What if your new rent is more than 10 percent higher?

The most logical move is not to rent the apartment in the first place.

If you are already a tenant, you have the right to challenge an excessive rent, by reporting it to the Federal Housing Office (BWO) by a registered letter, but you must do so within 30 days of signing the lease. 

You have to explain why you signed the contract, knowing the rent was excessive.