SC9 - Behavioral economics: a nudge for low-carbon mobility

At a time when the European Union is targeting carbon neutrality by 2050 (i.e., net zero greenhouse gas emissions), global CO₂ emissions from the transport sector, which represent a quarter of the total, are continuing to increase. To overcome this and address the climate emergency, technological improvements and carbon taxes do not appear to be enough. There also needs to be a change in behavior.

The FRAME¹ project relates to the incorporation of environmental considerations in the travel decisions of private individuals and focuses on new, less interventionist approaches as recommended in the literature, such as information and communication policies. The introduction of these “nudges”, the direct effect of which remains marginal, can have a significant impact in terms of both raising environmental awareness and complementing more interventionist policies (prices, taxes, regulations, etc.). One of the most well-known types of nudges is the framing effect which seeks to make communication campaigns more effective by associating with them with a suggestion to alter the perception of some aspects of the problem under consideration and influence the decision accordingly. For example, the consequences of a given type of behavior can be presented either in terms of expected gains, by adopting a change, or in terms of losses suffered as a result of not adopting it.

As part of the FRAME project, the effect of attribute valence framing,- i.e. a description of the same object (or characteristic) positively or negatively - was tested on individuals’ preferences to promote pro-environmental transport behavior via a DCE² [1], specifically designed for the purpose. Various analyses were conducted to determine whether this type of framing may or may not have an impact in terms of reducing transport-related CO₂ emissions. Easier to implement than traditional levers, such as taxes, nudges like this are not based on the strong assumption that individuals are entirely rational.

The DCE was conducted on a representative sample of the French population (age, gender, occupation: in total, 1,032 people aged between 18 and 75 living in mainland France). A hypothetical scenario was presented to participants, asking them to travel for a private purpose using public transit (domestic haul). The origin and destination of the trip were assigned, and two travel alternatives by means of public transit were proposed (see Table 1). 

Ten choice cards were presented to each respondent, with various combinations of travel time, cost, sanitary distancing and CO₂ emissions (see. Table 2).

The main framing effects studied were the gains and losses of two distinct attributes, namely travel time and CO₂ emissions.

Respondents were asked to make successive choices from the choice cards proposed with a view to having them reveal their preferences for the different attributes. The results were obtained using dedicated econometric and statistical methods associated with discrete choice models (see. [2] for more details). The coherence of the attribute coefficients was verified by analyzing their signs³ and relative values.

Firstly, it emerged from the analysis that respondents focused above all on trying to minimize the price and duration of their trip, with price being twice as important as duration, and then on maximizing the sanitary measures on offer. Even if the CO₂ criterion was ranked last, a negative coefficient has been observed, meaning that in general transit users do care about their emissions and seek to minimize them. 

Secondly, results indicated that a loss framing on travel duration or CO₂ emissions was significant and increased the weight of the framed attribute in the individual’s decision. On the contrary, this effect was not observed for gain framing. The loss framing effect is larger when applied to CO2 than to duration, which is a more familiar attribute.

In terms of public policies, two aspects emerge from this research. Firstly, we demonstrated that a loss framing on CO₂ emissions significantly increases the respondents’ choice of pro-environmental behavior, while a loss framing on duration increases the average preference for shorter trip duration; gain framing has no significant effect. This result needs further confirmation but, by providing a better understanding of travelers’ choice priorities, it could serve as a basis for the design of more appropriate pro-environmental policies. Secondly, we showed that the effect of loss framing was greater for CO₂ than for duration. One possible explanation for this finding is that framing on a more distant or complex attribute (e.g. kg of CO₂ emissions) has a greater effect than framing on an already well-known and typical attribute (e.g. duration). If so, it would be beneficial to find a way to communicate on CO₂ emissions with a more understandable unit of measurement.

¹- Project financed by ADEME (2021 - 2024): cadrage de l’inFoRmAtion pour la promotion d’une Mobilité durablE (framing of information for the promotion of sustainable mobility) In partnership with Gustave Eiffel University, Nantes University and Rennes University.
²- Discrete Choice Experiment
³- Relevance and statistical significance.
     

References:

1. Collet C., Gastineau P., Chèze B., Mahieu P-A., Martinez F. (2023), Combining economics and psychology: Does CO₂ framing strengthen pro-environmental behaviors ?, Ecological Economics, Volume 214.
   >> https://doi.org/10.1016/j.ecolecon.2023.107984
      

2. Chèze, B., Collet, C., Paris, A. (2021), Estimating discrete choice experiments: theoretical Fundamentals,
   >> Les Cahiers de l’économie n° 142, IFPEN Working Paper series.
         

Scientific contact: Benoît Chèze

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