8. GENERAL DISCUSSION
8.1 The Role of Psychology and Behavioural Economics in Tobacco Control Research Economic models and analyses have played the predominant role in guiding tobacco
price policy, one of the most fundamental and successful policies implemented worldwide (Chaloupka et al., 2011; Chaloupka et al., 2012; Dunlop et al., 2011; Gallet & List, 2003; Gallus et al., 2006; Hanewinkel & Insensee, 2006). However, by incorporating principles from psychological theory and experimental design, behavioural economic studies can make an important contribution to our understanding of addiction and tobacco control. Behavioural economic methods can generate price and consumption data over a broader range than can be assessed in the natural economy, provide a platform to evaluate the potential impact of introducing alternative products onto the market, compare important groups, and evaluate intra-individual differences in demand and addiction to better understand addiction processes and devise better interventions. Tobacco control research must take into account the dynamic global context in which policies are being implemented, including proposals for endgame goals in a number of countries and the rapid development of and increasing access to
alternative products. Behavioural economics provides a time- and cost-effective approach for evaluation of such changes, and there is a growing evidence base for the validity of
behavioural economic measures and methods.
8.1.1. Measuring demand for cigarettes. The research in this thesis provides additional support for the use of the CPT (MacKillop et al., 2008) for assessing demand for cigarettes. The demand curves generated by the CPT reported in Chapters 4 through 6 were characteristic of demand curves for inelastic commodities, with cigarette consumption mostly high but decreasing sharply at relatively high prices and eventually reducing to zero (Tucker et al., 2017; Tucker, Bullen, et al., 2017a; Tucker, Kivell, et al., 2017). This is consistent with the demand curves seen in previous studies using the CPT (Chase et al., 2013; Few et al., 2012; Johnson & Bickel, 2006; MacKillop et al., 2012; Mackillop et al., 2016; MacKillop et al., 2008; Murphy et al., 2011) and also with self-administration studies (Bickel, Degrandpre, Higgins, & Hughes, 1990; Bickel, Degrandpre, Hughes, & Higgins, 1991a; Bickel &
Madden, 1999; Johnson & Bickel, 2006). The exponentiated demand model (Koffarnus, Franck, et al., 2015) provided good fits to the demand data generated in all of these chapters (Tucker et al., 2017; Tucker et al., 2017a; Tucker, Kivell, et al., 2017) and demand metrics generated directly from the CPT and from fits of the exponentiated model highlighted relevant group differences for Māori/Pacific and New Zealand European smokers (Tucker, Kivell, et al., 2017). This was consistent with the greater reductions in cigarette consumption by Māori/Pacific smokers, especially males, reported after actual excise tax increases in New Zealand (Tucker et al., 2016). Although these two findings were not directly compared, Grace et al. (2014) found that a measure of local elasticity of demand derived from the CPT predicted actual changes in smoking behaviour after excise tax increases in the same sample, though they did not assess this by ethnicity. This supports that the CPT can provide
information about group differences in cigarette demand that may be used to evaluate the effectiveness of price policy for specific groups.
8.1.2. Measuring demand for alternative products. The studies in this thesis used simulated demand procedures to evaluate demand for alternative products, including an adapted CPT, which evaluated demand for the alternative product if available in isolation, and a cross-price task evaluating demand when available concurrently with regular cigarettes, but at a lower price. Previous research supports that hypothetical demand corresponds with actual purchasing and substance use behaviour (Amlung et al., 2012; Amlung & MacKillop, 2015; Bickel et al., 2009; Johnson & Bickel, 2002; Lagorio & Madden, 2005; MacKillop, Amlung, et al., 2010; Madden et al., 2003; Madden et al., 2004; Wilson et al., 2016). The validity of the CPT is well supported for regular cigarettes (Chase et al., 2013; Few et al., 2012; Grace et al., 2014, 2015a; MacKillop et al., 2014; MacKillop et al., 2012; Mackillop et al., 2016; MacKillop et al., 2008; Murphy et al., 2011). The research in this thesis is among the first to use a CPT to evaluate demand for alternative products: VLNC cigarettes (Tucker et al., 2017) and e-cigarettes (Tucker, Bullen, et al., 2017a).
Because VLNC cigarettes are virtually identical to regular cigarettes in their intended use and units for sale, it seems likely that the CPT would be a valid way in which to assess demand for these products. Conceptually, it may be anticipated that estimated consumption of VLNC cigarettes would be higher than for regular cigarettes, in an attempt to achieve optimal nicotine intake from a product containing a substantially lower dose. However, the opposite was found in Chapter 5; estimated consumption of VLNC cigarettes was lower (Tucker et al., 2017). This may indicate that preference and favourability may play a more important role in smokers’ decision to use these products, but it must be considered that the single use of VLNC cigarettes may have been insufficient for participants to make informed choices on the CPT and so estimates of demand may not be accurate. Nonetheless, there could be important
policy implications based on the simulated demand data, which are discussed in the next subsection.
It is less clear when the CPT is an appropriate way in which to assess demand for e- cigarettes due to more substantial differences in the product characteristics, patterns of use and units of pricing. E-cigarettes are ‘vaped’ in quite different patterns to cigarette smoking (Cooper et al., 2016; Dawkins, Turner, Roberts, et al., 2013; Pepper & Brewer, 2014) and involve a greater upfront cost for the e-cigarette itself and technical accessories, however prices range considerably for the e-liquid or cartridges. Thus, price “per 1-5 minute vape” which was used in attempt to provide an easier comparison with regular cigarettes for first- time e-cigarette users in Chapter 6 (Tucker, Bullen, et al., 2017a) is not likely to be the most realistic way to estimate vaping behaviour based on actual market costs. Cassidy et al. (2017) conducted focus groups with e-cigarette users and found that smokers reported that the relevant unit would be either price per cartridge or per measurement of e-liquid in millilitres (based on the different types of e-cigarettes used). However, it seems unlikely that this could be accurately estimated for first-time users who have no experience of how long such
measures would last. Although the unit used in Chapter 6 may not accurately capture patterns of use, results reported in Chapter 7 suggest that the mean number of ‘1-5 minute vapes per day’ reported (pertaining to actual daily e-cigarette use) corresponded with reported
remaining cartridges at the end of the two week period (Tucker, Bullen, et al., 2017b). This provides some tentative support for the simulated demand estimates for e-cigarettes generated by the CPT.
The studies in this thesis use a cross-price task from Grace et al. (2015b) to estimate cross-price elasticity for VLNC cigarettes and e-cigarettes. It is important to note that the CPE was based on a limited range and density of prices and may not have accurately estimated the shape of the function. As discussed in Chapter 5 (Tucker et al., 2017a), Hursh
and Roma (2016) proposed an extension of the exponential equation for fitting CPE which may provide a more accurate estimate of CPE based on a greater number of prices. However, the prices used here encompassed a relatively realistic range of prices (based on the New Zealand market price of cigarettes at the time of the study) and similar CPE estimates were found in Chapters 4 (Tucker, Kivell, et al., 2017), 5 (Tucker et al., 2017) and 6 (Tucker, Bullen, et al., 2017a) to those based on self-administration studies (Johnson & Bickel, 2003; Johnson et al., 2004; Shahan et al., 2000). This suggests that the CPE estimates obtained in this thesis may provide important information about the substitutability of these alternative products, though should be interpreted with caution.
8.1.3. Utility of subjective effects measures. Rees et al. (2009) propose that the commercial success of alternative products depends in part on consumer response to trialling and using these products. The aspects of consumer response considered in this thesis include various subjective effects, specifically Satisfaction (taste and enjoyment qualities),
Psychological Reward (withdrawal symptom alleviation), Aversion, and Craving Reduction. The studies in this thesis highlight the importance of considering the subjective effects of these products. In Chapter 5, the lower demand for VLNC cigarettes (relative to regular cigarettes) corresponded with poorer subjective effects ratings, suggesting that these factors may be a barrier to consumer use of VLNC cigarettes if they were to become available (Tucker et al., 2017). The studies in Chapters 6 and 7 showed that although subjective effects may change over time, both simulated demand and actual e-cigarette use behaviour can be predicted using a 2-factor subjective effects model (Psychological Reward and Satisfaction) (Tucker, Bullen, et al., 2017a, 2017b). This suggests that subjective effects may be an important factor in determining subsequent use of a product and may be important factors to study, particularly in the current context where multiple alternative products are becoming more and more available and accessible for smokers.