One straightforward way of addressing the problem would consist of policies that place legal limits on the extent to which rents may be increased. Yet, the idea of rent control faces outspoken opposition. Opponents often defend their view by pointing out that rising rents have an underlying cause in the shortage of supply of housing in a given area. Constraining rents, they argue, does nothing to alter the shortage of supply or, worse, exacerbates it by reducing the returns on investment for property developers, thus undermining the economic incentives for an increase in supply. This line of argument, however, appears unconvincing.
Shortages of supply in housing cannot easily be solved in the short term and are partly determined by geographical factors that cannot be altered at all. To the extent to which rent control policies fail to address the underlying problem of supply without worsening it, why should they not be considered as an interim measure? It is, of course, easy to conceive of policies that would further exacerbate the problem, for example if they took the shape of absolute rent ceilings that would make it impossible for developers to recoup their investment. There are, however, obvious policy alternatives that would place limits on rents and rent increases while being flexible enough to ensure a sufficient return on investment. In fact, if policies were structured such that returns on investment in new developments are higher than returns on investment in existing properties, they could create additional incentives for the construction of new homes, rather than undermining them. The very lack of rent controls, in turn, can be seen as compounding the imbalance between supply and demand in that it creates demand for existing properties on the part of speculative investors that would not exist if rent controls limited the returns on speculative investment.
A further prominent argument against rent controls, even if understood as second-best or interim measures, relies on the appeal of free markets as a mechanism for the allocation of scarce goods. If a good is in short supply and prices are left to move freely, they will rise up to the point at which an equilibrium is reached between the amount of goods available and the amount demanded at the price in question. From the point of view of economic theory, this process is often considered to be attractive on the basis that it ensures that scarce goods are allocated to those who value the good most highly. If the price was artificially kept low, in contrast, the allocation of goods would be determined by factors that may be less normatively appealing or left to pure chance. Applied to the present context, if there is a shortage of housing in a given location, would it not be a morally attractive outcome if tenants with the strongest preference for the location would get to live there?
Maybe it would. As an objection to the regulation of real-world housing markets, however, the argument is fundamentally flawed. The claim that equilibrium prices allocate goods to those who value the good most highly is plausible only in conjunction with the idealised assumption that the bidding parties are roughly equal in their ability to pay. In a real-world context in which potential tenants differ significantly in their wealth and thus their ability to pay, differences in willingness to pay rent cannot be taken as a direct reflection of the subjective value that a give property has to them. Since the absence of rent control measures does nothing to ensure that housing is allocated according to strength of preference, the appeal to this allocative ideal cannot serve as an objection against rent controls.
In the absence of other arguments, the controversy about rent controls appears to boil down to a conflict between the interest in affordable housing on the one hand, and the interest of property investors on the other. It seems clear to me that the interest in affordable housing is the morally weightier one. This is not meant to deny that investments made under existing rules may give rise to legitimate expectations. Honouring such expectations, however, should not prevent us from changing rules that apply to future investments.