Consumption-based indicators such as the energy and carbon footprint of households are largely determined by their spending levels. An inequality of household expenditures in a population therefore implies an inequality of their environmental footprints. Figures 1a-c show European households by decile of expenditure and their associated footprints for energy and carbon in 2015. The figures show that increasing expenditure generally translated into larger footprints, but that the inequality decreased from expenditure to energy to carbon, with 10:10 ratios (the top decile divided by the bottom decile) of `r exp_10_10`, `r energy_10_10` and `r co2eq_10_10`, respectively. Total expenditure ranged from `r exp_bottom_decile` trn€ to `r exp_top_decile` trn€ (or `r fd_pae_bottom_decile`€ to `r fd_pae_top_decile`€ per adult equivalent) across bottom and top decile, the energy footprint from `r energy_bottom_decile` EJ to `r energy_top_decile` EJ (or `r energy_pae_bottom_decile` GJ/ae to `r energy_pae_top_decile` GJ/ae), and the carbon footprint from `r co2eq_bottom_decile` MtCO2eq to `r co2eq_top_decile` MtCO2eq (or `r co2eq_pae_bottom_decile` tCO2eq/ae to `r co2eq_pae_top_decile` tCO2eq/ae). The reason for this is evident from figures 1d-f. Both the energy intensity of consumption, measured as energy use per € expenditure (d), and the carbon intensity of energy, measured as carbon per unit of energy use (f), gradually decrease from bottom to top expenditure decile. The weighted average energy intensity of consumption decreased from `r mean_energy_intens_bottom_decile` MJ/€ in the bottom decile to less than half (`r mean_energy_intens_top_decile` MJ/€) in the top decile. Additionally, the carbon intensity of energy was also higher in the bottom decile (`r mean_co2eq_of_energy_intens_bottom_decile` gCO2eq/TJ) compared to the top decile (`r mean_co2eq_of_energy_intens_top_decile` gCO2eq/TJ). There is a clear trend of decreasing intensities across expenditure deciles even though the variance in the lower deciles is much higher. The carbon intensity of consumption (figure 1e) combines the effects of the intensities of 1d and 1f. The higher carbon intensity of energy is likely due to a larger share of emission intensive energy carriers in the energy system. The decreasing energy intensity of consumption is due to either inefficient energy technologies or energy subsidies in lower-income areas in Europe.
```{r figure1, out.width="98%", fig.cap="Expenditure and environmental footprints and intensities across European expenditure deciles. Total expenditures (a), energy footprint (b), and carbon footprint (c) per decile. Energy intensity as energy footprint per expenditure (d), carbon intensity as carbon footprint per expenditure (e), and carbon intensity as carbon footprint per energy footprint (f)."}
```{r figure1, out.width="98%", fig.cap="Household expenditure and environmental footprints and intensities across European expenditure deciles. Total expenditures (a), energy footprint (b), and carbon footprint (c) per decile. Energy intensity of consumption as energy footprint per expenditure (d), carbon intensity of consumption as carbon footprint per expenditure (e), and carbon intensity of energy as carbon footprint per energy footprint (f)."}
In absolute terms, the various final consumption sectors contribute very differently to the total environmental footprint of households (Figure 3). On average, shelter and transport are the two largest sectors, accounting for nearly two thirds of both footprints. However, there are big differences between the sectors when looking at the respective contributions in the expenditure quantiles. For shelter there is almost no difference (neither in the carbon nor in the energy footprint). Especially the lower four expenditure deciles have high carbon emissions, which can be explained by the extreme differences in intensity shown in Figure 2. Transport was the most unequal sector, with footprints `r transport_energy_10_10` times higher in the top decile compared to the bottom deciles (corroborating findings in [@ivanova_quantifying_2020] and [@oswald_large_2020]). Manufactured goods was the second most unequal consumption category (10:10 ratios around `r man_goods_energy_10_10` for both footprints), followed by services (10:10 ratios of `r services_co2eq_10_10` for carbon and `r services_energy_10_10` for energy) and then food (10:10 ratios of `r food_energy_10_10` for both footprints).
In absolute terms, the final consumption sectors contribute very differently to the total environmental footprint of households (Figure 3). On average, shelter and transport are the two largest sectors, accounting for nearly two thirds of both footprints. However, there are big differences between the sectors when looking at the respective contributions of each expenditure decile. For shelter there is very little difference, in both the energy and carbon footprint, between deciles. The lowest four deciles even have higher carbon footprints from shelter than most higher deciles, which can be explained by the extreme differences in intensity shown in Figure 2. Transport was the most unequal sector, with footprints in the top decile `r transport_energy_10_10` times higher than the bottom decile (corroborating findings in [@ivanova_quantifying_2020] and [@oswald_large_2020]). Manufactured goods was the second most unequal final consumption sector (10:10 ratios around `r man_goods_energy_10_10` for both footprints), followed by services (10:10 ratios of `r services_energy_10_10` for energy and `r services_co2eq_10_10` for carbon) and then food (10:10 ratios of `r food_energy_10_10` for both footprints).
```{r figure3, out.width="100%", fig.cap="Energy and carbon footprints by final demand sector and European expenditure decile in 2015 further broken down by emission source location."}
```{r figure3, out.width="100%", fig.cap="Energy and carbon footprints by final consumption sector and European expenditure decile in 2015, further broken down by emission source location."}
