Annex

Annex

Estimation of the global number of vapers

Introduction

Estimates of the prevalence of vaping are critical to measuring the uptake and coverage of THR. However, information on the prevalence of vaping is still scarce in many countries.

WHO promotes the MPOWER tobacco control programme, the first letter of which refers to Monitoring. One of the key points of this is to collect up-to-date information on issues related to the use of tobacco and related products. Unfortunately, in reality this is a very difficult task for many countries due to costs. Collecting information about the value of a particular characteristic in a given population requires a representative survey based on a random sample. Such surveys are expensive.

Market data are available within companies and from market research and analysis companies such as EuroMonitor. However there is an unclear relationship between market size – by value or units sold – and the prevalence of vaping in the population.

 

Data availability

We have found information on the prevalence of vaping from 49 countries. There are two publicly-available international research programmes and eight national programmes on tobacco use and vaping.

The international research from which we collect data is: The Global Adult Tobacco Survey (GATS),274 last conducted in 2017, providing data on six countries (there are 25 of them in the study, but we used only six due to outdated surveys or not covering the subject of e-cigarettes); and the Special Eurobarometer on Attitudes of Europeans towards tobacco and electronic cigarettes275 from the European Commission, last conducted in 2017, gathering data from 28 countries.

There are also International Tobacco Control Surveys276 in 29 countries with data on e-cigarettes in six countries but we did not use it due to methodological issues (ie use of non-probabilistic samples).

National surveys on tobacco use and vaping (or at least having some information on this topic) include for example:

» National Drug Strategy Household Survey 2019 (Australia).277

» Healthy Ireland Survey 2017.278

» Malaysia 2016 National E-Cigarette Survey.279

» Encuesta Nacional de Consumo de Drogas, Alcohol y Tabaco (ENCODAT 2016-2017, Mexico).280

» Use of e-cigarettes among adults in Great Britain, 2019 (ASH UK).281

» Surveys from the Office for National Statistics (UK 2019).282,283

» National Adult Tobacco Survey (US).284

In addition, we have information from general surveys for seven other countries.

Surveys on vaping

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GSTHR 2020

Data were introduced in our database and maintained by the GSTHR research group. Quality controls – consisting of the continuous cooperation with regional informants around the world – are regularly performed to ensure that sources are updated, and data are introduced correctly.

 

Methods

 

Assumptions

Given that there is information for only 49 countries, the question arises as to how to estimate the prevalence of vaping in countries for which information is unavailable.

Where national data are unavailable, we have used an accepted epidemiological method of estimating country data by assumed similarity with other countries in the same region and economic condition for which data points are available. This methodology is commonly used for estimating health status in the absence of national surveys.285,286,287 It works in the same way as many methods used for statistical inference and analysis with incomplete data.

The main mathematical tool used for estimation was the method of average similarity.288,289,290 It assumes that if certain characteristics in a given group of countries are similar, we can assume that these countries will also be similar in other respects. This allows us to impute unknown values of the characteristics with the average values of those characteristics in the countries where they are known.

The quality of such estimation depends on the ratio of known and unknown fractions. The more known input data we use and the more homogeneous they are, the better result we will get. Table 1 shows the relationship between amount and internal differentiation of input data and quality of estimates.

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A further issue regards the availability and relevance of data on country characteristics from which similarity between countries may be inferred. We used the WHO region, the World Bank income classification and the legal status of e-cigarettes.

The second methodological problem is that surveys are conducted in different years and are often not repeated. Most of the available data allow for the calculation of an estimate for 2018 (most of the recent studies are from 2018 or before). Therefore, the data need to be adjusted to arrive at estimates for 2020. This can be done by reference to data on market growth. Based on publicly available “Statista” analyses,291 we can track changes in global revenues in the e-cigarette market. Assuming a linear relationship between market revenues and the number of users, we can estimate forward the global number of vapers in 2020.

This assumed relationship is unclear, as market values are affected by price and consumption patterns. Not every shift in the market affects 100 per cent of the number of users. It would be good for the quality of the projection to know what the real efficiency of the relationship between market data and the number of vapers is in the population. It can be easily calculated using the Pearson’s correlation coefficient and the data where both the local market revenue and the prevalence of vapers are known.

 

Estimation methods

Based on the available information, we calculated the average prevalence of vaping for the WHO region, World Bank income classifications and legal status of the sale of e-cigarettes. Unfortunately, as we could guess, some groups are very poorly represented. Low-income countries are represented only by Uganda. Uganda is also the only data point for the African region. Similarly, we have only one data point from the South East Asia region with Bangladesh and the East Mediterranean region with the United Arab Emirates.

Average prevalence of vaping by factors used in the estimation

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These three factors gave us four income groups, six regions and three sales statuses, which allowed us to separate 72 subgroups. For each of the groups the average prevalence of vaping was calculated. These 72 values were used as substitutes for the prevalence figures in the countries belonging to the group. Of course, not all subgroups were represented. For the first (1) – the most detailed, three-factor – subdivision we had information for only 13 subgroups, which allowed us to calculate estimates for 83 countries.

For the other countries, we had to use a two-factor breakdown covering all pairs of these three factors. A second (2) split was made on the basis of income groups and sales status, which gave us eight information cells covering 161 countries, a third (3) was made on the basis of income groups and regions with 10 information cells covering 142 countries and a fourth (4) was made on the basis of regions and sales status with nine information cells covering 102 countries. Last (5) subdivision was based only based on one income groups factor.

The results of the calculations have been placed successively in the blanks remaining after the previous step. This means that the countries remaining without an estimated value after the first step have been assigned the values generated in the second step. In the third step we filled in the missing values remaining after the second step and in the fourth step remaining after the third step. All remaining gaps were filled with the fifth step.

We started with 49 known countries. The first step increased this number to 83, the next to 161, next to 190, the fourth one gave us only three more countries, increasing the number of countries to 193, and the fifth to 198. There were still three countries left.
We attributed the average value obtained from all known countries to these countries.

Information growth at subsequent levels of the estimation process

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GSTHR2020

The number of vapers was calculated by taking as the denominator the total adult population (over 15 years old) obtained from the UN database for 2018.292

 

Adjustment of the estimate for market value changes between 2018 and 2020

 

Correlation between average revenue per capita and prevalence of vaping in UK

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E-cigarette use in England – Office for National Statistics. (n.d.). Retrieved 3 August 2020, from https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/healthandlifeexpectancies/datasets/ecigaretteuseinengland

E-Cigarettes – worldwide | Statista Market Forecast (adjusted for expected impact of COVID-19). (2020, May). Statista. https://www.statista.com/outlook/50040000/100/e-cigarettes/worldwide

Given the time lapse between when surveys were undertaken and 2020, it is necessary to estimate subsequent growth. The question is, what is the relationship between market growth and changes in vaping prevalence? We have information on this for the UK for the period 2011 to 2019. We have used market revenues per capita to avoid distortions related to population changes. As we can see in Figure 1, both trends were characterised by steady growth. The correlation between both time series was very strong. On the basis of this analysis, it can be concluded that the changes in the revenues from the vape market have influenced the prevalence of vaping products with 93 per cent efficiency. Then we assumed that this relationship is similar globally.

 

Results

The number of vapers in the 49 countries from which the survey data are derived is 40.3 million. We estimate that 17.8 million vapers live in the remaining 152 countries. This gives a total of 58.1 million vapers worldwide in 2018.

Main results of the estimate for 2018

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2.1 million vapers live in low income countries, 7.8 million in lower middle income countries, 19 million in upper middle income countries and 29.3 million in high income countries.

Estimated number of vapers by income groups for 2018

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4.1 million vapers live in the African region, 4.2 million in the Eastern Mediterranean region, 4.6 million in the South-East Asia region, 11.2 million in the Western Pacific region, 15.3 million in the European region and 18.7 million in the region of the Americas.

Estimated number of vapers by WHO regions for 2018

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38.6 million of vapers live in countries where sale of nicotine vaping products is allowed, 9.5 million in countries where sale of nicotine vaping products is banned and 10 million in countries where there is no specific law.

Estimated number of vapers by legal status of nicotine vaping products for 2018

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The projection for year 2020 was made on the basis of information from the E-Cigarettes Worldwide Statista Market Forecast.293 The global number of vapers estimate was fitted to revenue data at the 2018 time point (meaning revenue data from 2018 was directly paired with estimated number of vapers). In other words, the market trend was zeroed (calibrated) at 2018. The proportions series – centred at 2018 – was adjusted with the mentioned above coefficient of the correlation between market revenue and number of vapers.

Revenue trend in percents centered at 2018

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Multiplying subsequent proportions by the estimated global number of vapers, we have given projections of this number for other years. For the year 2020, the projection is 68 million vapers globally.

Estimated number of vapers by legal status of nicotine vaping products for 2018

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E-Cigarettes – worldwide | Statista Market Forecast (adjusted for expected impact of COVID-19). (2020, May). Statista. https://www.statista.com/outlook/50040000/100/e-cigarettes/worldwide

Discussion

We estimate that there are approximately 68 million nicotine vaping product users worldwide. However, this estimate should be treated with caution, as there is great uncertainty about some of the individual country estimates, and for 152 countries and territories data were missing. There is also variation in survey definitions of vaping. It is obvious from the data collected and assessed in our database that the available information is often of poor quality – survey samples are not numerous enough to provide sufficient precision to measure such small parts of the population. The sampling method of many studies is not probabilistic, which makes it impossible to generalise the measured values correctly per population. It is well known that monitoring risk behaviours in hidden populations is not straightforward. However, efforts to improve the accuracy of the information systems should be encouraged.

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