Introduction
The existence of a market grants its participants –both consumers and firms– benefits
known as producer and consumer surplus, which sum constitute social welfare[1].
Nevertheless, the sole existence of a market does not guarantee the maximum level of
social welfare, since it may culminate in various structures, such as perfect competition,
monopolistic competition, oligopoly, and monopoly.
1
Consumer surplus –in yellow in Figures 1a, 1b, and 1c– is constituted by the sum –integral with non-linear curves– of the
difference between the price each consumer is willing to pay –a point on the market demand curve– and the price he pays –
market price–; producer surplus –in blue in Figure 1a and blue plus red in Figures 1b and 1c– is constituted by the sum –
integral with non-linear curves– of the difference between the cost of producing one unit –a point on the market supply
curve– and the price at which it is sold –market price–.
Among all previous structures, the one that provides the maximum overall sum of benefits
to society, that is the maximum social welfare, is a competitive market. Specifically, as the
level of competition increases in any market the amount of production augments, the
variety and quality of products or services expand, and the prices drop (Biswas &
Koufopoulos, 2020; Broman & Eliasson, 2019; Nie & Yang, 2023). For example, a larger
competition in the banking market promotes an increment in the quality of financial
services, a reduction in their prices, a boost in the proportion of society with access to
these services (Lartigue Mendoza et al., 2020), a larger rate of economic growth, and a
better distribution of income (Abuselidze, 2021; Barra & Zotti, 2019; Hsieh et al., 2019).
With this in mind, the economic science has analysed the existent relationship among
diverse economic variables and developed a set of mathematical instruments that permit
measuring how far existing markets are from being competitive and how much market
power firms have for setting prices above marginal costs in a profitable way; putting it
differently, how much power firms have for choosing a price and earn more than they
would do in a competitive market.
Some of these mathematical instruments have been addressed to measure the level of
concentration, which refers to the number of firms and their relative participation in a given
industry or market. Usually, the more concentrated a market is, the less efficiency and
social welfare it achieves, punishing consumers and rewarding anti-competitive practices.
In this regard, Rodríguez-Castelán et al. (2023) and Liu et al. (2022) argue that a higher
concentration affects negatively firms´ productivity, given that if only a few enterprises
dominate a market the competition is limited, permitting firms to operate with less
pressure for improving their products, services, and processes.