Increasing Salad Consumption Using Dynamic Social Norms   

Executive Summary

Nudge Lebanon, in collaboration with students from the American University of Beirut (AUB), designed and implemented an intervention that utilized an innovative behavioral change technique known as dynamic social norms to increase the consumption of salads at a local restaurant in Beirut. According to the results, informing customers about the growing trend of vegetable consumption in Lebanon increased salad orders by over 20 percentage points compared to a control group. These results provide promising evidence on the effectiveness of dynamic social norms in prompting individuals to make sustainable food choices.

Policy Challenge

Meat production is a primary cause for climate change leading to increased carbon emissions, loss of wildlife loss and greenhouse gases^[1]. Meat production has increased worldwide by up to five-fold between 1961- 2014 with Asia recording the highest increase^[2]. This increase is also reflected in Lebanon as livestock imports increasing by 7.2% on average every year between 2010 and 2014^[3].

A survey that was conducted in Lebanon on 444 individuals in 2006 showed that young people (25-34 years) ate significantly more meat, sugar, and consumed significantly less cooked vegetables and legumes. The meat intake of the sample showed that the consumption of the butchery products was the highest with 47.6 g per day followed by poultry^[4]. While many ascertain that the increase consumption in meat is due to the traditional Mediterranean diet, it is worthy to note that many of the Lebanese population is aware of the importance of fruits and vegetables in their daily diets^[5].

With this in mind, Nudge Lebanon, in collaboration with students from the AUB, designed an intervention to increase vegetarian food and salad consumption at a local restaurant using dynamic social norms – the provision of information about how other people’s behavior is changing over time^[6].

Intervention Design

The intervention was implemented during lunch time on weekdays (between 12:00 pm and 3 pm) at a local restaurant in Beirut, and lasted for 3 weeks. A total of 103 tables (45 control, 58 treatment) were randomly assigned to complete a brief survey on consumers’ opinion towards a trending issue, in exchange for a $1 voucher that can be redeemed at the restaurant^[7]. Treated tables received information on the increasing trend of vegetable consumption in Lebanon (see Figure 1), while the control group received information about the changing patterns in social media usage (see Figure 2). Both the control and treatment tables were asked to give their opinion about these trends in a few words. The aim of the survey was to trigger thoughts among the treated tables about the trending consumption of vegetables in Lebanon, therefore priming diners to order vegetarian-based dishes, namely salads.

Figure 1 – Dynamic Social Norms Group

Figure 2 – Control Group

Results

Table receipts were collected by the team on a daily basis. Tracking of receipts was facilitated using color coded vouchers that identified the treated and non-treated tables. The restaurant staff were instructed to staple the voucher to the relevant receipt. The outcome of interest is a binary variable that takes the value of 1 if a salad dish was ordered on the table and 0 otherwise.

As expected, the results show that informing customers about the growing trend in vegetables consumption in Lebanon (i.e. the dynamic social norms group) significantly increased the probability of a salad being ordered on a table by 20.1 percentage points (p-vale = 0.047) compared to the control group (treatment tables: 60% vs control tables: 39%).

Figure 3 – Proportion of tables ordering at least one salad dish (n = 103)

These results were robust to the addition of controls for the day of the week, albeit with weaker significance (p = 0.077). Adding other variables such as the number of customers per table generate stable results with significance remaining below the 10% level.

Conclusion

The results provide promising evidence supporting the use of dynamic social norms to nudge individuals into making sustainable food choices, particularly the consumption of salads. The relatively large effect suggests that communicating growing trends in social behaviors may translate into substantive positive behavioral change.

Further experiments should be conducted in different domains and with larger samples to determine the robustness and limitations of using dynamic social norms in different contexts.

Endnotes

[1] Park, T., & Schein, A. (2019). Can we be more Ambitious on Sustainable Diets? How what we eat can help us reach net zero emissions. Behavioral Insights Team.

[2] Ritchie, H., & Roser, M. (2017). Meat and seafood production & consumption. Our World in Data.

[3] Analysis of Lebanon’s Food Market (2016). BankMed Special Report. Retrieved from https://bit.ly/2lErj7G

[4] Nasreddine, L., Hwalla, N., Sibai, A., Hamzé, M., & Parent-Massin, D. (2006). Food consumption patterns in an adult urban population in Beirut, Lebanon. Public health nutrition, 9(2), 194-203.

[5] Sacre, Y. & Saliba, R. & Bohme, M. (2015). Evaluation of Fruit and Vegetable Consumption as Phytonutrients Potential in Lebanon. Retrieved from https://bit.ly/2kqaZY1

[6] Sparkman, G., & Walton, G. M. (2017). Dynamic norms promote sustainable behavior, even if it is counternormative. Psychological science, 28(11), 1663-1674.

[7] In addition to incentivising diners to complete the survey, the use of vouchers facilitated the tracking of receipts from treated and non-treated tables, such that vouchers were color coded according to the condition that the table was assigned to.