missolivialouise:

Some good information and graphics in the article on how most existing duplexes, triplexes, and fourplexes only exist because they were build before current zoning laws were enacted. 
Neighborhoods all across America would benefit from changing zoning to allow more “missing middle housing” to add more small-scale density.

More neighbors means more tax base to draw from for things like road repair, public transportation, and other public amenities. More neighbors also means more people to support and keep alive local businesses.

But unfortunately, most zoning favors the single-family house. And that’s a big part of why many small local businesses struggle to stay afloat, and most public transportation systems suck.

Low-density Zoning Threatens Neighborhood Character