This is a fair point except that neighborhoods are not fungible and are in short supply.

You’re assuming that there is another 3/10 neighborhood available for the people who are displaced to move to, and therefore they gain a short term benefit and eventually end up back where they were.

In practice it’s typical that older areas which have become run down have ample city services, such as transit, parks, and libraries, which may not be the best quality, but at least exist.

Since neighborhoods are no longer built with these amenities, the best available substitute for someone who is displaced from an old neighborhood may be far less desirable than what they had before - a 1/10 trailer park, or worse, homelessness.

However, if we would continue to build traditional neighborhoods that were walkable, had city services, had transit etc. and built enough of those to keep up with the demand, then it would be much more likely that your scenario would play out. In that case the harm of economic change in neighborhoods would be greatly reduced, perhaps even to the point that it wouldn’t be a problem anymore

But that’s quite far from the reality on the ground today.

Transit comes with density and growth and usually increases in property values. When an area goes downhill but still has this services it creates a temporary situation that people can take advantage of certain aspects - live with increase crime but get increased services.

The wealth of yesterday created that situation. At some point someone will invest in that older area because of the location value.

The only way to artifically control that is through low rent units. Which create other barriers because one can never leave or they give up something even though it might make sense to move somewhere else for family or job reasons. When they always take 1/3 of gross getting a raise and taking on more responsibility seems counter-productive. Hard to break dependence.

moving is not just a reversion to the mean. A neighborhood is more than atomized individuals who live there. There can be a community of people which form a network and a support system that is many years old. Pricing certain people out can rip apart these communities, so it's not just a matter of relocating then continuing as you were.

Then there are the individual-level logistical problems. What does moving do to your commute? Is it easy to find a new job? Will your kids have to go to a different school district?

> people owning houses

This is the part you're overlooking. People in undesirable communities are renting because they don't have that generational wealth built up

Even if people aren't renting, once the desirability goes up, developers are going to want to kick you out, and will use the government to do it.

Your model is mostly useful and shared with the people with the 'harm' view. To reach the conclusion that the 'harm' group are reaching, set your move transaction cost¹ to a large value and add a local-relationships parameter that depends on time-spent-at-current-location and weight it very highly as well.

Should you so desire, you may want to add in a cost to capture the notion of how a person moving contributed to the improvement. This will usually need to be inflated above the true economic contribution (IKEA effect, etc.).

The local-relationships parameter may be effectively quadratic (since a person moving diminishes their relationships and relationships are two-sided).

¹ It is clear you know this but for other readers that may not, that's not just the monetary cost.

> Can someone explain what this description misses and where the harm comes from?

If they have lived somewhere a long time, one of the big losses is: Relationships.

For the people forced to move, they will not find another "3 out of 10" neighbourhood, as part of what makes it a 3 is that's where all their friends and long-lasting relationships and perhaps childhood memories are. That already makes anywhere else < 3.

They will have to move somewhere where they likely don't know anyone, or at least not the well-established friendships they had before.

If they have extended family in the area, they will have to leave those too. (Parents, children, aunts & uncles, siblings, that sort of thing).

Those friendships and relationships aren't just valuable for sentimental reasons. They form an essential practical support structure, and sometimes a financial support structure. For many people those things are a big part of what makes quality of life.

And they might be forced to move at an age where it's difficult to make new friends, especially deep friendships.

As people on the lower end of the socio-economic ladder, it's likely that they were benefitting from their friendship/relationship network in another, subtler way: By having good quality relationships with people higher up the ladder, their own circumstances are effectively lifted up as well.

For example, they might be taken out to places and introduced to opportunities and people because of long-lasting friendships with people richer than themselves. Their children get to play with children of richer friends with nicer houses to stay over in. Little things that probably translate to differences of opportunity when the children are older. That kind of uplift goes away when they move to another location.

Some people have a good relationship with a local employer too, and will lose that as well. It might be something quite treasured (even though it presumably doesn't pay well), and difficult or impossible to replace. Remember we're talking about people forced to leave, not those who want to leave.

The community also depends on the people living in it - a diversity of the types, and incomes, of people benefits the neighborhood. People churning in and out is harmful -- I'd argue more harmful than the increased property value accounts for.

I don't have a good solution for this. Rent control helps a bit, but has bad externalities. Property ownership helps a lot but any measure to drive up ownership immediately prices out lots of people because it's captured very well by the housing market.

Too logical. Here's what non-owners might see:

"The neighborhood is improving, things will get more expensive". Bad.

"I have to move now." Bad. "This new neighborhood is worse than my old one." Only half true (they started at 3 and ended at 3), but perceived as bad.

or instead of dismissing people's grievances as illogical, you can skip the strawman phase and engage with the real issues as I and others have described here

The post I replied to logically argued that people are not harmed when their community improves and they are priced out and forced to move. (Note, I never claimed they were illogical, but instead that they were "too logical" Pure logic will not explain why people feel the way they do, because people are not always logical).

They then ask:

> Can someone explain what this description misses and where the harm comes from?

In answer, maybe no harm is actually done. But even so, people will perceive that they have been harmed. And in the larger context of this thread, that is why people are sometimes unhappy with their community being improved, because they believe it will price them out and harm them.

> In answer, maybe no harm is actually done. But even so, people will perceive that they have been harmed.

Maybe cows can fly. Maybe a lot of things. But it does cause harm. So your idea about people's perceptions seems condescending

> but perceived as bad

There is no good or bad except in terms of someone's perceptions.

>Can someone explain what this description misses and where the harm comes from?

Empathy. Sense of place is real. Home isn't just your house or property values. People deserve not to be priced out of their homes so the sake of profit.