Status competition, inequality, and fertility: implications for the demographic transition

Abstract

The role that social status plays in small-scale societies suggests that status may be important for understanding the evolution of human fertility decisions, and for understanding how such decisions play out in modern contexts. This paper explores whether modelling competition for status--in the sense of relative rank within a society--can help shed light on fertility decline and the demographic transition. We develop a model of how levels of inequality and status competition affect optimal investment by parents in the embodied capital (health, strength, and skills) and social status of offspring, focusing on feedbacks between individual decisions and socio-ecological conditions. We find that conditions similar to those in demographic transition societies yield increased investment in both embodied capital and social status, generating substantial decreases in fertility, particularly under conditions of high inequality and intense status competition. We suggest that a complete explanation for both fertility variation in small-scale societies and modern fertility decline will take into account the effects of status competition and inequality.

Keywords: demographic transition; fertility; inequality; social complexity; social status; status competition.

Figure 1.

An illustration of the effect of ecological parameters on the core mechanics of the model. The left-hand column represents conditions of lower inequality in the inputs to social rank (the distribution in panel (a)), while the right-hand column represents conditions of higher inequality (the distribution in panel (e)). Panels (b,f) indicate the rank achieved for a given level of investment in social capital. Panels (c,d,g,h) plot parental fitness as a function of investment in social capital given different values for the inflection point (, varying across the solid and dashed lines) and slope (ρ, varying across panels) of the effect-of-social-capital function. Solid black points indicate the optimal (fitness-maximizing) levels of investment in social capital.

Figure 2.

(a–f) Mean fertility as a function of inequality in the inputs to status (CV(ɛ), varying across the horizontal axis) and the inflection point (, varying across the dashed and solid lines) and slope (ρ, varying across panels) of the effect-of-social-capital function.

Figure 3.

(a–d) Dynamics of fertility and investment in offspring quality through time in four different ecologies. The thick solid line plots mean fertility, the dotted line plots mean investment in survival-and-productivity capital (a), while the thin solid line plots mean investment in social capital (). The left-hand column represents lower inequality in the inputs to status (CV(ɛ) = 0.4), whereas the right-hand column represents higher inequality (CV(ɛ) = 1). The top row represents a lower intensity of status competition (), whereas the bottom row represents a higher intensity (). ρ is held constant at 2.5 across ecologies.

Figure 4.

The predicted effect of increasing status competition on fertility with a shift from pre- to post-demographic transition ecological conditions. We hypothesize that fertility falls across the demographic transition not only due to an increase in the gains to direct investment in productivity, but also due to an increase in investment in status competition. The grey curve shows the effect of increasing gains to direct investment in productivity alone. The dashed black curve shows the additional effect of increasing inequality in the inputs to status, while the solid black curve shows the additional effects of increasing both inequality and the intensity of status competition. (The gains to direct productivity investment are assumed to increase for all three curves. For simplicity, other factors that we recognize as important, such as reduced infant mortality rates, are not explicitly modelled. See the electronic supplementary material for a description of the model parameters used to generate this plot.)