On Displacement

All renters move, and often. Partially it's a response to changing conditions (employment, family size) but also in response to being able to take advantage of a better deal (better rent, better quality, better location) elsewhere. So renters (per se) aren't displaced. When people talk about displacement, they are talking about the displacement of an ethnic community--when a traditionally Black / Mexican / Jewish / Chinese / Irish / Italian / Greek / Korean / Hmong / Ethiopian community ceases to have a majority of that ethnicity, typically because a wealthier, whiter, less immigrant population is moving in.  

If the housing stock is is fixed, newcomers inevitably displace incumbents, in a zero sum game that always sees the incumbents outbid. And over time, the decline in the size of the ethnic community population can no longer support 'specialty' services, markets, grocers, and (eventually) churches. And that is a loss. As strands are pulled away, the fabric of a community dissolves. And it's not something that can be casually recreated, because it's an both: a) an emergent property of a density of recurring interactions with a single spatial & temporal locus; and also b) the product of the purposeful effort by past community leaders (even if you've got dry tinder, it still takes someone to strike a match).   

There is a disjunction in community norms about acceptable behavior - newcomers vs incumbents. And the newcomers are of the hegemonic in-group, they have the law on their side (de facto or de jure), endangering incumbents through exposure to the police. 

So when people talk about displacement, we should be clear on what that means and what that requires: Enough NIMBY* to prevent new rising rents from being matched with new development, and a zero-sum game reducing the ethnic population below the threshold necessary to support specialty stores and services.  

*There is nothing more NIMBY than a parking requirement--people fighting the addition of new people or businesses, excluding them simply to prevent competition for a limited resource that they have no legal claim or right to exclude.