How is discriminating by age reasonable? Not all 20 year olds are booking for 15 people. If someone lies about the number of people attending, then kick them out.

Car insurance providers discriminate against young drivers for similar reasons: you're more risky. I wouldn't entrust the care of my entire house to college students.

You can say that about blacks (esp males): they're more risky. Just because you're not supposed to look at those actuarial tables, doesn't mean it's not a statistical reality.

Maybe the car insurance example was bad, but I think the situation is a little more complex than pure statistics.

The US has a very long history of racism against minorities. It's been difficult to get a strong system in place to combat racism. Ageism against young people has a built in correction system called aging.

But what if black people at any age are more costly investment than white people at any age?

But is that not what the review system is for? What prevents a host from reviewing potential guests' history on a case-by-case basis to determine their level of risk?

Black men are more risky because of a history of systemic racism forcing them into situations where they need survival and status systems outside of the law. Young people are more risky because young people are impulsive and stupid. So it seems appropriate to treat these two things differently.

So why are men more risky than women, over their entire lives?

It's almost like there can be different reasons for behaviors that seem parallel on the micro level...

There are a bunch of college students who own and care for houses that are better than yours.

I'm sure there are, but it's kind of standard that most 18-21 year olds have only 1-2 years experience in an independent apartment/house. Just like 17 year olds typically only have 1 year experience driving.

I wouldn't even rule it out entirely, you'd just need references (a decent rating).

The same age group is faced with similar problems renting apartments because they often lack credit ratings and previous references.

For many purposes it would be cost prohibitive to run detailed background checks on individuals to discover every relevant fact like that, so they rely on aggregates, which works well enough.

And when race is one such aggregate?

I personally don't think it's reasonable, but our society deems it acceptable to do so

> How is discriminating by age reasonable?

Well, for one thing, its not generally expressly prohibited by law.

Since when is what's reasonable the law, or what the law is reasonable?

Minority opinion here, but not all discrimination by race is bad and allowing people to discriminate by race/community can actually have desirable effects.

For example: If I'm American, I might donate to a service that helps American homeless, and would not have donated otherwise if the service was global.

Similarly, If I'm black, I might donate to a service that only helps blacks and would not have donated otherwise. If I'm Caucasian and feel a strong sense of community for my heritage I might do the same, etc.

People feel more sympathy to those they can relate with -- I don't think that will change for many years.

And to add to what oh_sigh said, what makes you think that the reasons for discriminating by gender are valid? In my country (the USA) we passed laws decades ago making precisely that (discrimination in lodging based on gender) illegal.

If the situation were renting out a stand-alone apartment or house, I agree entirely. Gender discrimination is unwarranted.

In situations where you're renting a bed or a room in a shared common space — I don't think it's unreasonable to be more selective about gender. Is it discriminatory for colleges to not group men/women together in dorm room?

Again, look at the severity disparity here:

would it be socially acceptable for a woman to say "I don't want a male roommate?"

would it be socially acceptable for a white person to say "I don't want a black roommate?"

> Is it discriminatory for colleges to not group men/women together in dorm room?

No, but that's not relevant. The correct analogy would be "Is it discriminatory for colleges to refuse residence to one gender?" That said, I respect the right of anyone to choose who they let into their home, even if I might disagree with the criteria.

Residence and co-habitation is a meaningful distinction. AirBnB provides both services.