Abstract
Reducing meat consumption is considered to have great potential to mitigate food-related greenhouse gas (GHG) emissions. I conducted a field experiment with two restaurants to test if nudging can increase the consumption of vegetarian food. At the treated restaurant, the salience of the vegetarian option was increased by changing the menu order and enhancing the visibility of the vegetarian dish. The other restaurant served as a control. Daily sales data on the three main dishes sold were collected from September 2015 until June 2016. Results show that the nudge increased the share of vegetarian lunches sold by on average 6 percentage points, and that the treatment effect increased over time. The change in behavior is partly persistent, as the share of vegetarian lunches sold remained 4 percentage points higher after the intervention ended than before the experiment. The intervention reduced GHG emissions from food sales by around 5 percent.
Generated Summary
This research study examines the effectiveness of a “nudge” strategy to decrease meat consumption in a university restaurant setting. The study employs a field experiment involving two restaurants at the University of Gothenburg, Sweden. The core methodology involves altering the food environment at one restaurant (the treated restaurant) by changing the menu order to place vegetarian options at the top and increasing the visibility of vegetarian dishes, while the other restaurant served as a control. The study’s scope encompassed collecting daily sales data on main dishes from September 2015 to June 2016 to test if nudging increases vegetarian food consumption and if these effects are persistent. The research also aims to evaluate how the nudge’s impact changed over time and the changes in GHG emissions connected with the changes in food consumption patterns. The study employs a difference-in-differences (DiD) approach and a before-after analysis to estimate the treatment effect.
Key Findings & Statistics
- The livestock sector contributes approximately 14.5 percent of global human-induced greenhouse gas (GHG) emissions yearly.
- Meat consumption is causing about one-third of food-related GHG emissions emerging from consumption in Western countries such as Sweden and the United States.
- Reducing meat consumption is seen as a way to protect biodiversity, land, and freshwater ecosystems.
- Reducing meat consumption can yield significant benefits for both public health and the environment.
- Per capita meat consumption in Sweden has constantly risen since the 1990s to a record-high 87.7 kilograms (kg) per person in 2016.
- In general, food is responsible for around one-fourth of the consumption-based emissions of an average US household.
- Approximately 8 tons of CO2 equivalent (tCO2e) per capita emerge from private consumption in Sweden, of which 2 tCO₂e relate to food. Of those, 0.7 tCO2e can be attributed to meat consumption.
- The study’s intervention increased the share of vegetarian lunches sold by on average 6 percentage points.
- The change in behavior is partly persistent, as the share of vegetarian lunches sold remained 4 percentage points higher after the intervention ended than before the experiment.
- The intervention reduced GHG emissions from food sales by around 5 percent.
- In a representative World Wildlife Fund (WWF) survey, 37 percent of the respondents state that they will cut their meat consumption in order to reduce their climate impact during the coming year, and 33 percent state that they have already done so during the previous year.
- The treated restaurant had an average of 152 warm lunches a day throughout the year, while the control sold on average about 140 dishes.
- The share of vegetarian dishes sold at the treated restaurant increased from 14% to 20% after the intervention.
- The share of vegetarian dishes sold at the control restaurant remained stable at around 26%
- The before-after comparison showed that the share of vegetarian dishes sold significantly increases by 6.2 percentage points.
- The DiD estimates of the treatment effect lie between 6 and 7.3 percentage points.
- A minimum treatment effect of 6 percentage points represented a 43 percent increase in the share of vegetarian lunches sold, compared with the baseline period, as the result of the nudge.
- The nudge led to an increase of 0.8–0.9 percentage points in the share of vegetarian dishes sold each week.
- The sales share of meat 1 dishes decreased by around 10 percentage points, and the meat 2 dish increased by around 4 percentage points in period 1.
- The share of vegetarian lunches is still around 4 percentage points higher than in the baseline period.
- In terms of average CO2 equivalents (CO2e) emitted per kg of meat sold in Sweden, 1 kg of beef causes the highest emissions.
- Emissions with the nudge in place were 4.8 percent lower than they would have been without the intervention.
- During the reversal period, emissions were still 3.8 percent lower than they would have been if there had been no intervention in period 1.
- Total emissions are reduced by 0.7 and 8.5 percent in different scenarios.
Other Important Findings
- The study’s intervention involved moving the vegetarian option from the middle of the menu to the top and increasing its visibility.
- The research also included a control restaurant to compare changes with the treated restaurant.
- The study collected daily sales data on three main dishes to measure changes in consumption.
- The study analyzed the data across three experimental periods: a baseline, an intervention, and a reversal period.
- The study examines how the effects of the intervention developed over time.
- The research considers the impact of the nudge on vegetarian dishes in the control restaurant.
- The study examines substitution effects by considering all three dish types: vegetarian, meat 1, and meat 2.
- The study explores heterogeneous effects by analyzing the impact of the nudge on various types of vegetarian dishes.
- The study also calculates the intervention’s impact on GHG emissions.
- The study considered the impact of a new chef in the control restaurant, with implications of this staff change on the analysis.
- The study found that in the control restaurant, there was a significant negative effect of -2.4 percentage points from listing the vegetarian dish in the middle instead of at the top.
- The increase in the sales share of vegetarian dishes was accompanied by a decrease in meat 1 dish by about 10 percentage points and an increase in the meat 2 dish by about 4 percentage points.
- The study indicates that changing the menu order may lead to a switch to vegetarian food, but also away from it.
Limitations Noted in the Document
- The study acknowledges that the results might not be generalizable to populations with different demographic characteristics, particularly older populations.
- The study design did not allow for a complete separation of the impacts of menu order changes and increased visibility.
- The analysis does not account for factors like individual dietary habits, making it difficult to predict the nudge’s effect size in different settings.
- The study relies on the assumption that changes in the control restaurant reflect exogenous factors and that parallel trends existed before the intervention.
- The study’s conclusions about heterogeneous effects are limited by the relatively low frequency with which each category was served.
- The study acknowledges the limitations in data, such as relying on averages for standard portions and assuming equal dairy input across dish types.
- The study did not allow for analysis of the total sales impacts, the data did not include sales changes from the previous year.
Conclusion
The field experiment demonstrates the potential of “nudging” as a tool to promote more climate-friendly food choices. The study’s primary finding is that making vegetarian dishes more salient through menu modifications can significantly increase their consumption. The intervention at the university restaurant, which involved placing vegetarian options at the top of the menu and improving their visibility, led to an increase in vegetarian lunch sales. A noteworthy aspect of this study is the sustained effect of the intervention; the increased share of vegetarian dishes remained elevated even after the intervention concluded, suggesting potential for habit formation. The research highlights the importance of analyzing how interventions work over time, showing that the impact of nudges can evolve and persist. The study also demonstrates the potential to measure and estimate the impact of these interventions in reducing GHG emissions in a real-world setting. While the study found that the intervention successfully reduced meat consumption and had a positive impact on the sales of vegetarian options, the research also recognized limitations. One key aspect is the challenge of isolating and understanding the effect of changing the menu order or enhanced visibility. The study also points out the challenges with external validity, given the specific demographics of the population (students and employees in a university setting). In addition, the authors discuss that this approach is costless for the restaurant and may not affect profits negatively. The study’s findings suggest that the nudge’s success may depend on the setting and population. The authors suggest that transparency in implementing such interventions is essential, and changes to the food environment should be communicated to the customers. Overall, the research underscores the significance of designing and implementing environmental interventions in food choice, showing a way to promote more sustainable dietary behaviors.