Are There Any True "Natural Monopolies" Left in Infrastructure?

The existence of perhaps some 83 U.S. “whole community” municipal internet access networks, plus 400 to 600 dark fiber networks, networks serving business districts and cooperatives does continue to raise questions of whether home broadband networks are natural monopolies; whether they are forms of utility infrastructure or not; and if so, how they ought to be regulated and funded. 

Patterns for supplying electricity, water, wastewater, trash collection can take the form of “municipal ownership” or “private supply.” Roads, railroads, airports, seaports, oil and gas pipelines likewise can take a variety of forms, ranging from functional “natural monopoly” to “competitive supply” markets. 

Over time, however, the range of infrastructure considered to be natural monopolies has shrunk, In fact, many would consider most forms of infrastructure to be amenable to at least some competition by multiple suppliers in a single market, at the level of retail delivery and “last mile” networks.

Infrastructure Service	Market Model	Natural Monopoly?	Reasons
Airports	Oligopoly or Regulated Monopsony	Not necessarily	Multiple airports can serve a single region.
Seaports	Oligopoly or Regulated Monopsony	Not necessarily	Similar to airports, multiple ports can compete for cargo traffic based on location, efficiency, and infrastructure. Government regulation or dominance by shipping companies can also create a monopsony.
Roads	Public Good or Regulated Duopoly/Oligopoly	Generally a “natural” monopoly, but toll roads supplement	Roads are generally considered a public good as they benefit all citizens and cannot be easily excluded from use. Government funding and construction eliminates competition directly, while private tolls create limited competition between toll roads and non-tolled options.
Electricity	Regulated Monopoly or Partial Liberalization	Generally a local network monopoly in terms of retail delivery	Grid infrastructure requires high upfront investment and economies of scale, making a single regulated provider potentially efficient. However, renewable energy and distributed generation are introducing competition in electricity generation and retail markets.
Oil and Gas Pipelines	Regulated Monopoly or Oligopoly	generally a local network monopoly in terms of retail delivery	Similar to electricity, pipelines benefit from economies of scale and often operate as regulated monopolies in specific regions. However, competition can arise from alternative energy sources and competing pipeline infrastructure.
Mobile Service	Oligopoly	No	Several mobile providers typically compete in a given region, offering different plans, coverage, and network speeds. However, barriers to entry (spectrum licenses, infrastructure costs) can create an oligopoly with limited competition.
Home Broadband	Oligopoly or Duopoly	No	Similar to mobile service, a limited number of providers (cable, fiber, DSL) often compete in a given area. Government intervention can incentivize additional competition through infrastructure investment or regulation.
Waste Collection	Municipality, Oligopoly, or Competition	Generally no	Waste collection can be provided by a single municipality, several private companies competing in an oligopoly, or fully open to competition depending on local regulations and policies.
Wastewater Systems	Public Good or Regulated Monopoly	Yes, typically, at the retail level	Similar to roads, wastewater treatment is often considered a public good due to its environmental and public health benefits. Government funding and operation typically eliminate competition, while private involvement may occur through regulated contracts.

Half a century ago it was the prevailing wisdom that such networks were “natural monopolies” where the economics would only support one provider in each market. That was never the belief for mobile service provider networks, which have featured multiple suppliers since the start.