eLetters

519 e-Letters

  • By ignoring the impact of a vaping tax on smoking, the paper misses the most important point

    NOT PEER REVIEWED
    I would like to make three comments by way of a brief post-publication review.

    1. The impacts of vaping tax on smoking have been completely overlooked

    For a study of e-cigarette taxation to have any public health relevance, it must consider the impact of e-cigarette prices on *cigarette* demand. Cigarettes and e-cigarettes are economic substitutes. The demand for one responds to changes in the price of the other, an idea well understood in economics and quantified through the concept of cross-elasticity. The paper appears to pay no regard to the impact of vaping taxes on cigarette demand, Yet such effects might easily overwhelm any benefits from reduced e-cigarette use - in fact, impact on demand for other tobacco products and the development of informal markets are by far the most important impacts of a vaping tax. By way of example, a 2020 paper by Pesko et al. [1] concluded:

    "Our results suggest that a proposed national e-cigarette tax of $1.65 per milliliter of vaping liquid would raise the proportion of adults who smoke cigarettes daily by approximately 1 percentage point, translating to 2.5 million extra adult daily smokers compared to the counterfactual of not having the tax."

    2. The case for reducing adult vaping by taxation has not been made

    The authors have based their paper on an unexamined assumption that it is a justifiable goal of policy to lower rates of adult e-cigarette use. Why should...

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  • Scientific Concerns

    NOT PEER REVIEWED
    I have a number of concerns with the paper as currently written.

    1) The authors write: “Besides, none of the previous studies except Pesko et al (15) that examined the associations between vaping product excise tax adoption and ENDS use has accounted for the clustering of respondents within the same localities…” This is not accurate, as citation 19 also clusters standard errors at the locality level in all specifications.

    2) The authors write: "A working paper reported reduced ENDS sales, but not ENDS use prevalence or behaviours, after implementation of a vaping product excise tax policy. (19)” This is not accurate, as the cited study uses the magnitude of e-cigarette tax values, rather than an indicator variable for tax implementation. States have adopted e-cigarette taxes of different magnitudes and a number of them (such as California) have changed the magnitudes of these taxes after adoption. All of this variation is used in citation 19, contrary to the current study’s description. It's also unclear from the sentence whether citation 19 studied use and found imprecise estimates, or did not study use. It's the latter and this should be clarified. It's also unclear why the authors did not use magnitude of e-cigarette taxes themselves in the current paper, as has been commonly done in the referenced literature.

    3) Authors write they use a “nationally representative sample of US young adults.” I do not beli...

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  • In Response to Clive D Bates' Comments "By ignoring the impact of a vaping tax on smoking, the paper misses the most important point"

    NOT PEER REVIEWED

    We appreciate the comments from Bates and the opportunity for us to respond and clarify.

    First, Bates' argument heavily relies on the assumption that e-cigarettes and combustible cigarettes are substitutes, which is theoretically possible as some consider vaping as a harm reduction alternative to combustible cigarettes. Empirically, however, there have been mixed findings about whether e-cigarettes and combustible cigarettes are substitutes (or complements). Bates cited Pesko et al. (2020) that concludes e-cigarettes and combustible cigarettes are substitutes, whereas other studies have shown that they are complements. For example, Cotti et al. (2018) found that higher cigarette excise taxes, in fact, decrease sales of both e-cigarettes and combustible cigarettes, suggesting that they are complements. Such mixed results abate Bates' argument that taxing ENDS could lead to more use of combustible cigarettes.

    Second, Bates might have ignored that our study focused on young adults aged 18-24 years rather than general adults when examining the effect of vaping product tax on e-cigarette use. Although Pesko et al. (2020) suggests that e-cigarettes and combustible cigarettes are substitutes, the findings are based on the general adult population (average age: 55 years) which may not be generalizable to the young adult population. In fact, one study conducted by Abouk and Adams (2017) indicates that e-cigarettes and combustible ci...

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  • In Response to Michael Pesko's Comments "Scientific Concerns"

    NOT PEER REVIEWED
    We thank Pesko for his comments and the opportunity for us to respond and clarify.

    First, we appreciate Pesko’s clarification that Cotti et al. (2020) clustered standard errors to account for clustering. In the present study, we used multilevel analysis not only to account for clustering of respondents (i.e., design effects) but also to incorporate different error terms for different levels of the data hierarchy which yields more accurate Type I error rates than nonhierarchical methods where all unmodeled contextual information ends up pooled into a single error term of the model.

    Second, we understand that Cotti et al. (2020) evaluated the magnitude of e-cigarette tax values, which does not contradict to our statement because our study focused on the effects of e-cigarette excise tax policies on individual e-cigarette use and prevalence rather than aggregated sales at state or county levels. We also clearly described the reason why we examined the e-cigarette excise tax policy implementation indicator rather than its magnitude in our paper’s discussion section.

    Third, our study used a nationally representative sample of young adults (rather than a nationally representative sample of general adult population). While we understand Pesko’s concern that a sample’s representativeness might be lost when subgroups are explored, we believe our use of sampling weights in analysis has reduced such a concern.

    Fourth, in Table 3,...

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  • Response to Clive Bates' critism of our article

    NOT PEER REVIEWED

    Clive Bates’ commentary on our paper repeats claims we previously addressed [1]. Here, we address seven points, the first is contextual and the remaining are raised in his letter.

    1. We note the failure of the author to acknowledge Māori perspectives, in particular their support for endgame measures, concerns in relation to harm minimisation [2] as outlined in his “all in” strategy, and ethical publishing of research about Indigenous peoples. [3]

    2. We reject the assertion that the basis of our modelling is “weak”. While there is uncertainty around the potential effect of denicotinisation, as this policy hasn’t been implemented, there are strong grounds to believe that it will have a profound impact on reducing smoking prevalence. This is based on both theory and logic (i.e., nicotine is the main addictive component of cigarettes and why most people smoke), and the findings of multiple randomized controlled trials (RCTs) showing that smoking very low nicotine cigarettes (VLNCs) increases cessation rates for diverse populations of people who smoke [4-7].

    Our model’s estimated effect on smoking prevalence had wide uncertainty, namely a median of 85.9% reduction over 5 years with a 95% uncertainty interval of 67.1% to 96.3% that produced (appropriately) wide uncertainty in the health impacts. The derivation of this input parameter through expert knowledge elicitation (EKE) is described in the Appendix of our paper. Univariate se...

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  • Multiple criticisms of this simulation

    NOT PEER REVIEWED

    I have published a summary critique of this modelling exercise on PubPeer. [1] This summarises concerns raised in post-publication reviews of this paper while it was in pre-print form by experts from New Zealand and Canada, and me. [2][3]

    By way of a brief summary:

    1. All the important modelled findings flow from a single assumption that denicotinisation will reduce smoking prevalence by 85% over five years. Yet the basis for this assumption is weak and disconnected from the reality of the market system being modelled.

    2. The central assumption is based partly on a smoking cessation trial that bears no relation to the market and regulatory intervention that is the subject of the simulation. Even so, the trial findings do not support the modelling assumption.

    3. The central assumption also draws on expert elicitation. Yet, there is no experience with this measure as it would be novel, and there is no relevant expertise in this sort of intervention. Where experts have been asked to assess the impacts, their views diverge widely, suggesting that their estimates are mainly arbitrary guesswork.

    4. The authors have only modelled benefits and have not included anything that might be a detriment or create a trade-off. The modelling takes no account of the black market or workarounds. These are inevitable consequences of such 'endgame' prohibitions, albeit of uncertain size. Though it may be challenging to mo...

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  • Scientific concerns

    ¶ The authors make some points in their article that are reasonable: 1) the generalizability of San Francisco's flavor ban compared to other places is an open question, and 2) the original study uses the San Francisco ban effective date rather than enforcement date. The original author (Friedman), who does not accept tobacco industry funding and is a well-respected scientist in the field, had pointed to both facts in her original article. So that information isn’t new.
    ¶ The current authors appear to construct a straw man argument claiming that Friedman argued that she was studying the effect of San Francisco enforcing its flavor ban policy. Friedman specifically wrote in her original article that she was studying, “a binary exposure variable [that] captured whether a complete ban on flavored tobacco product sales was in effect in the respondent’s district on January 1 of the survey year.” She specifically uses effect in the above sentence, so there is no ambiguity that she is studying effective date. San Francisco’s flavor ban effective date was July 2018 (Gammon et al. 2021).
    ¶ The authors found new information that the San Francisco YRBSS survey was collected between November to December of 2018. Gammon et al. 2021 (Appendix Figure 1) shows that flavored e-cigarette sales declined in San Francisco between the effective date and the end of August 2018 (compensating for a 30-day look-back period for the YRBSS question wording), even though the flavor ban...

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  • In Reply: Youth tobacco use before and after flavoured tobacco sales restrictions in Oakland, California and San Francisco, California

    Pesko’s central argument is that it does not matter that Friedman’s assessment of the effect of San Francisco’s ban on the sale of flavored tobacco products is not based on any data collected after the ban actually went into force. In particular, Friedman’s “after” data were collected in fall 2018, before the ordinance was enforced on January 1, 2019.[1] Pesko incredibly argues that Friedman’s “before-after” difference-in-difference analysis is valid despite the fact that she does not have any “after” data.

    Pesko justifies this position on the grounds that the effective date of the San Francisco ordinance was July, 2018. While this is true, it is a matter of public record that the ordinance was not enforced until January 1, 2019 because of the need for time for merchant education and issuing implementing regulations.[2]

    Friedman is aware of the fact that the enforcement of the ordinance started on January 1, 2019 and used that date in her analysis. In her response[3] to critiques[4] of her paper, she stated “retailer compliance jumped from 17% in December 2018 to 77% in January 2019 when the ban went into effect.” Friedman thought the YRBSS data was collected in Spring 2019; she only learned that the “2019” San Francisco YRBSS data she used were in fact collected in fall 2018 from our paper.[1]

    Rather than simply accepting this as an honest error and suggesting Friedman withdraw her paper, Pesko is offering an after-the-fact justification for the cl...

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  • Remaining scientific concerns unaddressed by authors

    NOT PEER REVIEWED
    In their response to my reply, the authors appear to not address mistakes in their analysis. It's important that any inaccurate statements be corrected for the benefit of other researchers trying to learn from this conversation. 1) The authors say in their response (and the paper) that there is no "after" period in the Friedman study. However, as reported by Gammon et al. (2022), there was an immediate decline in e-cigarette sales in San Francisco at the effective date. The authors need to explain how they can say there is no "post" period if other research clearly shows that e-cigarette sales declined starting July 2018. This is a central part of their argument and the paper unravels if there actually is a reduction in July 2018 as has been documented previously. The authors mention in their reply that they are aware of changes beginning in July 2018 ("merchant education and issuing implementing regulations"). The press may also have widely covered the effective date, which led to changes in youth's demand for e-cigarettes. Many retailers may have wished to become compliant immediately rather than wait until enforcement. All of these are valid potential mechanisms explaining why e-cigarette sales declined starting July 2018. So for the authors to say that Friedman doesn't have a "post" period is ignorant of both the literature and many valid reasons explaining why e-cigarette sales declined at...

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  • Friedman's Use of a Pre-Post Study Design was Appropriate

    NOT PEER REVIEWED
    After seeing the response from the authors of “Youth tobacco use before and after flavored tobacco sales restrictions in Oakland, California and San Francisco, California” to the Rapid Response, “Scientific Concerns,” I was dismayed by the reply of the authors that dismissed the efforts of fellow scientists to rigorously discern the effects of flavored tobacco sales restrictions. The central point of their critique of Friedman’s paper is that it only contains pre-flavored tobacco product sales ban datapoints. Hence, a pre-post difference-in-differences design is inappropriate. Friedman most certainly had post-data in her sample. Despite the criticisms from Liu et al, they have not unseated her primary contribution; after a policy change, youth tobacco use behavior in San Francisco changed. Liu et al. provide no rigorous counter-analysis on this point. The author’s argument that no behavior had changed in San Francisco during YBRSS data collection in late 2018 falls apart at close inspection.
    First, Liu et al. claim the flavored tobacco sales ban was not yet affecting retailer behavior in late 2018. This question is binary; it can either be answered yes or no. As of July 21, 2018, it was not legal to sell flavored tobacco products in San Francisco. No grace period was in place. Sales of all prohibited flavored products plummeted in the months after the policy became effective (Gammon et al., 2021 ; Table S1). However, sales did not reach zero,...

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