The implementation effects of different plastic bag ban policies in China: the role of consumers’ involvement

This study selects three cities in China that implement plastic bag ban policies with different levels of consumer involvement to compare the effects of policy implementation. In general, consumer plastic bag usage behaviour becomes more environmentally friendly when plastic bag ban policies became more stringent. High consumer involvement policies induces changes in pro-environmental bag use; however, their plastic-reducing effects are uncertain and compounded. In contrast, low-consumer-involvement policies could reduce plastic waste damage but could not make consumers’ more environmentally conscious with regard to bag usage. Moreover, this study confirms robust bag usage differences across different groups of consumers. These findings provide valuable insights into the patterns of influence of different types of plastic bag bans. Based on these insights, plastic crisis managers can create more effective and targeted policies to combat the growing plastic crisis.


Introduction
Plastic bags, one of the most widely used plastic products, have witnessed over 5 trillion in annual consumption worldwide (The World Counts 2023). Because of this heavy use, they have become a large source of ocean pollution and have caused the deaths of millions of marine animals (World Wildlife Fund 2021). When degraded into micro-plastics, they can return to the human body through the consumption of seafood (Rochman et al 2015), posing a significant threat to human health. The alarming environmental damage caused by plastic bags has sparked various tools such as legislation and levies from over 127 national governments to reduce consumer usage (Giacovelli 2018). Following this trend, extensive research has been conducted to evaluate the effectiveness of plastic bag bans in various countries. These studies are conducted either by observing consumers' bag usage changes before and after policies' execution (Thomas et al 2019, Wang and or by conducting surveys or interviews with residents to obtain their bag usage patterns or perceptions of plastic bag ban policies (Adane andMuleta 2011, Zambrano-Monserrate andRuano 2020). For instance, Convery et al (2007) found a 94% decline in plastic carrier bag usage owing to Ireland's 2004 plastic bag tax (€0.15 for each bag). This promising change prompts similar taxes in other countries, and most of these taxes produce a significant reduction in plastic carrier bag usage (He 2012, Madigele et al 2017, Martinho et al 2017. These pricing-based policies aim to induce behavioural changes. However, there are also material-based policies, such as those in China's Sanya, that decouple consumers from involvement by making plastic bags biodegradable and keeping prices the same as before. From this perspective, plastic bag bans that vary in consumer involvement may show different patterns and effects when modifying consumer behaviour. However, to date, existing studies have focused primarily on evaluating the effectiveness of a single policy (Poortinga et al 2013, Baxter et al 2022 Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. of these policies varies across different groups of consumers. These details warrant additional research efforts because they are critical to the design and improvement of plastic bag ban policies.
China, one of the world's largest consumers of plastic bags, introduced two national plastic bag ban policies, in 2008 and 2020, to crack down on the increasingly severe plastic crisis. The 2008 policies required all retailers to charge their consumers for the plastic carrier bags they used at the point of sale (General Office of China State Council 2007). In 2020, the Chinese government introduced tougher plastic bag ban policies, which required that by the end of 2020, all supermarkets in major cities be prohibited from using non-biodegradable plastic carrier bags (BBC News 2020). However, these policies are now implemented differently across China. For instance, China's major cities may execute the 2020 policies well, but small cities may disregard the new rules and implement the 2008 plastic bag ban policy. In view of this, this study selects three cities in China with different plastic bag ban policies to compare their patterns of influence on consumer bag usage. Figure 1 illustrates a typical shopping cart widely used in China and the three different types of bags investigated in this study. As shopping carts can be used as alternatives to carrier bags, this study classifies them as reusable bags for the analysis. Old plastic bags can be either plastic carrier bags or inner packaging plastic bags. Using old plastic bags is pro-environmental because it avoids the need for new bags. Therefore, based on the plastic-reduction effects, the degree of environmental friendliness of using the four types of bags is ranked as follows: shopping cart = reusable bags > old plastic bags > new carrier bags. The findings of this study could provide valuable insights into the patterns of influence of various plastic bag ban policies across China and reveal how different groups of consumers respond to these policies. These insights could prepare government officials and plastic crisis managers to deal with the worsening plastic crisis.

Study design and data collection
Three cities in China that implements different plastic bag ban policies are selected for analysis. Yangzhou is the first city, which serves as a base case as it still executes the 2008 plastic bag ban policies and provides cheap nonbiodegradable plastic carrier bags (charged RMB 0.3-0.8). Shanghai is the second selected city, which implemented the national 2020 plastic bag ban policies and required all its retailers to sell only biodegradable plastic carrier bags (charged RMB 1.0-1.8) in 2020. In 2021, Shanghai issued tougher plastic bag ban policies, forbidding the use of plastic carrier bags and requiring all supermarkets to provide only much more expensive (RMB 3.0-39.0) cloth or nylon carrier bags. The third city is Sanya, a famous tourist city located in southernmost China. The city requires all its supermarkets to provide only biodegradable plastic bags and charge for plastic carrier bags at similar prices to Yangzhou. Based on field observations and carrier bag prices, Shanghai's 2021 policies rank first regarding policy toughness, followed by Shanghai's 2020 policies, Sanya, and then Yangzhou. This study recorded the number of reusable bags, old plastic bags, and charged carrier bags used by consumers at the exits of supermarkets in all three cities. As we were unable to obtain the exact age of the observed consumers, we recorded their generation and gender. Specifically, a consumer was classified into the middle-young generation if he or she was younger than 60 years and into the old generation otherwise.

Case studies 1 and 2 in Shanghai
The first two case studies investigated the same nine supermarkets in Shanghai, China, from July to September 2020 and from late January to February 2021 between 17:30-19:00, when people were off work and available to do grocery shopping before dinner. Data collection was repeated thrice for each site to reduce potential bias caused by data collection errors. The two people responsible for data collection were trained in bag counting. The Cohen's α value for counting reliability was satisfied with a value of 0.82.

Case study 3 in Yangzhou
This study collected data from seven branches of a popular supermarket in Yangzhou between 15:30-17:00 and 17:30-19:00, in November 2021. To increase data reliability, the third case study conducted two sets of data collection at the same place. With a much smaller population size of about 4.5 million (Jiangsu Provincial Bureau of Statistics 2021), the city does not have as many supermarket brands as Shanghai. Instead, most Yangzhou residents chose one popular supermarket for shopping, which has branches distributed across every district of the city. Therefore, this study selects seven branches from each district for analysis.

Case study 4 in Sanya
The fourth data collection was conducted in Sanya between 15:30-17:00 and 17:30-19:00 in November 2021. With an even smaller population size of about 1.03 million (Hainan Provincial Bureau of Statistics 2021), the city also has limited brands of supermarkets. Similarly, we found a popular supermarket with branches in all four districts in Sanya. Therefore, six branches covering all districts of the city were investigated. Figure 2 shows the average use of each type of bag per purchase in the four cases. Generally, when plastic bag bans become more stringent, consumer bag usage becomes more environmentally friendly. As shown in figure 2, consumers from the Shanghai 2021 case increase their use of reusable bags and old plastic bags, and reduce their purchase of charged carrier bags as a result of policy. For instance, the use of reusable bags increases 3-fold from 0.162 to 0.446, when the plastic bag ban policies strengthened from Yangzhou's basic level to Shanghai's toughest level in 2021. Considering old plastic bags, Shanghai's 2021 case performs the best, with over 20% of its customers carrying reusable bags for shopping. However, in Yangzhou and Sanya, the reuse rate of old plastic bags is approximately 5%. For charged carrier bags, their average usage rate is 16.5% in Shanghai, which has the toughest policies in 2021, while with the least tough plastic bag ban policies in Yangzhou, their usage is the heaviest, with more than 50% of consumers purchasing at least one plastic carrier bag per purchase.

Bag usage with different plastic bag ban policies
To verify the significance of the bag usage changes between case studies in figure 2, this study conducted the Kruskal-Wallis (KW) test. As shown in table 1, except for the use of old plastic bags between Yangzhou and Sanya, all comparisons of bag usage are significantly different. Therefore, the observed change patterns shown in figure 2 are statistically supported.

Consistent bag usage difference between females and males
Despite the significant difference in number and type of consumer bag used among the four cases, the usage difference based on genders is consistent regarding reusable bags and old plastic bags. As summarised in table 2, female consumers consistently use more reusable bags and old plastic bags than male consumers. When the policies become more stringent, as in Shanghai in 2021, the usage pattern for charged carrier bags splits between the two genders. When the prices for plastic carrier bags are reasonable (e.g. RMB 0.3), bag use is no different between genders in the Shanghai 2020 case. However, when the bags are priced prohibitively high (e.g. RMB 39.0), both genders start to reduce their usage. Reduction by males (by 36.5%) is substantially lower than that of females (by 58.7%).

Robust bag usage difference between middle-young and old generations
In general, the middle-young and old generations consistently show similar use patterns for reusable bags and charged-carrier bags throughout the case studies. As summarised in table 3, regardless of the toughness of the plastic bag ban policies, the old generation uses significantly more reusable bags and purchases significantly fewer charged carrier bags than the middle-young generation. When carrier bags are cheap in Yangzhou and Sanya, the two generations use the same amount of old plastic bags (approximately 5%). However, when carrier bags are priced much higher in Shanghai, the two generations are disproportionately affected by these price increases, with the old generation showing heavier use of old plastic bags than the middle-young generation.

Influence of different factors on bag usage behaviour
To compare the impact of different factors on consumer bag usage behaviour, this study assigns an environmentally friendly value to each bag usage behaviour and examines the influence of gender, generation, and policy toughness in different cases. Specifically, reusable bags is assigned three points, reusing plastic bags is assigned two points, purchasing plastic carrier bags is assigned negative one point, and the environmental friendliness value of bag usage behaviour is measured as the sum of the above bag usage conditions. Regarding  policy toughness, the toughest Shanghai 2021 policy is assigned four points, and the least tough Yangzhou policy is assigned one point. Table 4 summarises the means, SD, and correlation values of the model variables. Table 5 summarises the results of ordinary least squares (OLS) regression. As M2 shows in table 5, all three factors significantly impact the environmental friendliness of bag usage behaviour, and generation exerts the largest influence (b = 0.677, p < 0.001), followed by policy toughness (b = 0.437, p < 0.001) and gender (b = −0.399, p < 0.001). Specifically, the old generation is more likely to engage in environmentally friendly bag usage behaviour than the middle-young generation. Females are also more environmentally friendly based on behaviour than are males. When plastic bag ban policies become tougher, consumer bag usage behaviour become more environmentally friendly.
4. Discussion 4.1. Mentality and shopping habits: the primary origin of persistent bag usage differences between genders and generations Although the four datasets of the study cases are significantly different, all their results support the same bag usage differences across genders and generations. We ascribe these robust differences to the mentality gaps between the different groups of consumers. For different genders, this study finds that male consumers use significantly fewer reusable bags and old plastic bags than female consumers use, regardless of the toughness of the plastic bag ban policies (see table 2). The finding of male consumers' lower usage of reusable bags is consistent with the findings of Thomas et al (2019) and Zambrano-Monserrate and Ruano (2020), who also argue that males are less likely to use reusable bags than females. This difference probably arises from males' reluctance to behave like females because of the traditional mentality that carrying a reusable bag for shopping is feminine (Brough et al 2016). As a result, males may continue to purchase new carrier bags (Sharp et al 2010) and use them significantly more often than females. As for different generations, this study finds that old consumers purchase significantly fewer charged carrier bags and use more reusable bags than middle-young consumers in  Notes: N = 14,721, Gender: 1 = male, 0 = female, Generation: 1 = old generation, 0 = middle-young a p < 0.05 b p < 0.001. the four cases (see table 3). The difference in consumption mentality and shopping habits between the two generations potentially supports this finding. The old generation grow up in significantly worse economic circumstances than the middle-young generation. For many elderly consumers, especially those in their 70s and 80s, saving money or thrifting has become a natural habit in their daily lives. Even if their economic conditions improve, they continue attempting to avoid unnecessary expenditure. For middle-young consumers, the cost (e.g., 0.5 RMB) for a carrier bag seems negligible compared with their total expenditure ). Therefore, middleyoung consumers may prefer to spend a small amount to avoid the 'inconvenience' or 'trouble' of carrying a reusable bag when shopping. It has become increasingly important for plastic crisis managers to overcome the traditional mentality of male usage of reusable bags. Marketing tactics, such as designing reusable bags in men's style, can work as a solution.

Implementation effects of different plastic bag ban policies: consumer involvement plays a role
Compared to Yangzhou's 2008 plastic bag ban policies, the policies in Shanghai and Sanya adjust to the new demand for plastic reduction from the national 2020 plastic bag ban policies. However, their policies differ in terms of consumer involvement and how plastic waste is reduced. In Shanghai, consumers are designed to participate in the plastic reduction process, and the effects of these policies depend on or require behavioural changes from consumers. As one of the most well-known metropolitan cities in China, Shanghai performs well in environmental management and public education (Dong et al 2018). For instance, the government launched a strategic plan in 2023 to build a zero-waste city (Shanghai Government 2023). Moreover, public spaces in Shanghai are filled with pro-environmental media and slogans. Through this powerful pro-environmental publicity, consumers in Shanghai are therefore more involved in reducing plastic bag usage than consumers in Sanya and Yangzhou. Conversely, by pricing carrier bags prohibitively high, Shanghai's policies succeed in manoeuvring consumer bag usage in a more environmentally friendly direction, for example, by bringing reusable bags with for shopping . In contrast, Sanya's policies decouple consumers from policy involvement by keeping all policies the same as before, except for changing the materials of all plastic bags to biodegradable ones. For consumers in Sanya, compared to the price increase, this material change is almost negligible, and they do not have to change accordingly. As a result, Sanya's bag consumption remains unchanged from that of Yangzhou and shows no signs of improvement. Therefore, Shanghai's policies perform much better than Sanya's in terms of inducing pro-environmental behavioural change, which is an important measure of environmental policy success (Nelms et al 2022). However, these two types of policies may result in a tie in terms of reducing plastic waste damage. In Sanya's case, the environmental damage from extensive bag usage would certainly be reduced by making all plastic bags biodegradable. Conversely, in Shanghai, the effects of reducing plastic waste damage depend on consumers' reduced use of all types of plastic bags. However, side effects were observed during data collection when consumers switched from their consumption of charged carrier bags to free inner plastic bags. Because inner plastic packaging bags are not designed for transporting goods, consumers prefer to use multiple bags in place of carrier bags, one tucked inside the other, to make them more durable. Therefore, the net effects of Shanghai's policies on the overall plastic reduction are ambiguous and complicated. Thus, for plastic crisis managers or government officials, knowing which type of policy is better suited is important. The answer lies in policy execution and consumer behavioural changes. Policies using biodegradable plastic bags shows promise for reducing plastic waste damage without causing any 'inconvenience' or 'sacrifice' to consumers. In this situation, consumers fail to develop pro-environmental bag usage habits, and once policy execution loopholes exist (e.g. some supermarkets still provide free regular plastic bags), the policy loses its plastic-reducing effects without making any progress in consumers' behaviours toward green bag usage. By contrast, by pricing carrier bags highly and through powerful pro-environmental publicity, Shanghai's policies could successfully induce pro-environmental behavioural changes.

Greener bag usage by female consumers and old consumers
All case studies in this study support the view that females and elderly consumers have greener bag usage behaviours compared to their counterparts. Specifically, female consumers carry significantly more reusable bags and old plastic bags than male consumers do. Elderly consumers carry more reusable bags and purchase fewer carrier bags than middle-young consumers. For the old versus middle-young generation comparison and for the female versus male comparison, the mentality difference best explains the robust bag usage differences. For instance, male consumers' less frequent use of reusable bags is highly likely given their deep feminine association with carrying reusable bags for shopping (Brough et al 2016, Thomas et al 2019.

Policies with high consumer involvement produce greener bag usage behaviours
By comparing consumer bag usage under four different plastic bag ban policies, this study finds that policies requiring high consumer involvement could, in the long run, induce more pro-environmental bag usage habits than those requiring little involvement. Moreover, charging high prices for plastic carrier bags increases the cost of no-bag shopping. In this case, consumers will receive an adverse stimulus if they enter stores without shopping bags. This adverse stimulus promotes and strengthens consumers' behavioural changes because they want to avoid unpleasant future experiences or extra costs (Skinner 1938). A key point is that this adverse stimulus works well only when prices are sufficiently high.

Limitation and future research
This study is limited by the number of supermarkets investigated in the three selected cities. Future research should increase the number of supermarkets and include more cities. Furthermore, the intrinsic arbitrariness of giving scores to each bag type is a limitation of this study. Future studies are encouraged to better measure the degree of environmental friendliness regarding bag usage. The observational data recording method also fails to uncover the motivations or other psychological reasons behind consumer bag usage behaviour. Future research are encouraged to address these limitations.

Data availability statement
The data cannot be shared publicly on publication as it will be used for future research. The data that support the findings of this study are available upon reasonable request from the authors.