Article Text

Exposure of 4-year to 24-year olds to tobacco imagery on prime-time Chilean television
  1. Armando Peruga1,2,3,
  2. Oscar Urrejola1,4,
  3. Iris Delgado1,
  4. Isabel Matute1,
  5. Carla Castillo-Laborde1,
  6. Xaviera Molina1,
  7. Macarena Hirmas1,
  8. Andrea Olea1,
  9. Claudia González1,
  10. Ximena Aguilera1,
  11. James D Sargent5,6
  1. 1Centro de Epidemiología y Políticas de Salud, Universidad del Desarrollo Facultad de Medicina Clínica Alemana, Las Condes, Chile
  2. 2Tobacco Control Research Group, IDIBELL, Barcelona, Spain
  3. 3Consorcio de Investigación Biomédica en Enfermedades Respiratorias-CIBERES, Madrid, Spain
  4. 4Subdirección de investigación, Teletón, Santiago, Chile
  5. 5C Everett Koop Institute, Geisel School of Medicine, Lebanon, New Hampshire, USA
  6. 6The Dartmouth Institute for Health Policy & Clinical Practice, Dartmouth College Geisel School of Medicine, Hanover, New Hampshire, USA
  1. Correspondence to Dr Armando Peruga, Centro de Epidemiología y Políticas de Salud, Universidad del Desarrollo Facultad de Medicina Clínica Alemana, Las Condes, Chile; aperuga{at}udd.cl

Abstract

Introduction The extent of the population’s exposure to tobacco imagery across all genres of regular TV programming and the contribution of each of these genres is unknown, except for UK broadcast channels. The objective of this study is to estimate the exposure of young people to tobacco imagery on Chilean prime-time television and the programme source contributing to such exposure.

Methods Programmes aired during 3 weeks in 2019 from the 15 highest audience channels in Chile were content-analysed for the occurrence of tobacco categorised as actual use, implied use, tobacco paraphernalia, tobacco brand appearances and whether they violated Chilean smoke-free law for each 1 min interval (92 639). The exposure of young people to tobacco content was estimated using media viewership figures.

Results Young people received 29, 11 and 4 million tobacco impressions of any type, explicit use and smoke-free violation, respectively, at a rate of 21.8, 8.0 and 2.1 thousand impressions per hour of TV viewing. The main sources of exposure to tobacco impressions were feature films and animated productions, which were almost entirely non-Chilean. Finally, young people were exposed to tobacco brand impressions primarily through films, effectively circumventing the advertising ban in Chile.

Discussion Television programming is a source of significant youth exposure to tobacco imagery, including branding impressions. To conform to the WHO FCTC, Chile should prohibit tobacco branding in any TV programme and require strong anti-tobacco advertisements prior to any TV programme portraying tobacco.

  • advertising and promotion
  • media
  • public policy
  • prevention

Data availability statement

Data are available on reasonable request. Data are available on request from the Centro de Epidemiología y Políticas de Salud of the Universidad del Desarrollo 3 years after the end of data collection (June 2019).

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

Statistics from Altmetric.com

Background

Chile has the highest prevalence of current adult smoking in the world (age-standardised 45.0%), only after Nauru and Kiribati1 and the world’s highest prevalence of current cigarette smoking among females 13–15 years of age (26.4%), on par with Palau.2 The high prevalence of smoking in Chile is at odds with the relative strength of its tobacco control policies (Chile’s MPOWER score ranked 14th in a list of 195 WHO Member States and territories).3 Moreover, Chile has implemented some of these policies for more than a decade, including large health graphic warnings since 2006, a steady increase in excise taxes since 2008,3 4 strong smoke-free policies5 since 2013, which are well-enforced indoors6 and a ban on tobacco advertising. One unregulated element is the depiction of tobacco in audiovisual products, the focus of the present study.

Exposure to tobacco imagery in movies has been associated with smoking initiation, reinforcing tobacco use among smokers, especially adolescents and young adults, and facilitating the relapse of ex-smokers.7 8 We are not aware that the behaviour associations vary across channels of dissemination, for example, movie theatres versus television. However, the exposure to tobacco occurrences depends on image density and reach of the media channel. Tobacco imagery in audiovisual products like movies has the potential to reach far larger audiences through television than through theatres alone. In Chile, the exposure potential on television is considerable since two-thirds of the population watches television daily (the average time is 5.5 hours per day).9 While youth rely more on internet streaming and video-on-demand than adults, they still receive most of their video consumption from traditional airing channels.9

The present study estimates exposure of 4-year to 24-year olds to tobacco imagery on Chilean prime-time television. More specifically, it quantifies the number of onscreen tobacco occurrences and the number of tobacco impressions received by those aged 4–24 years, who are most susceptible to such imagery. The study also determines the factors associated with higher exposure to tobacco imagery on TV to prioritise the tobacco control measures that have not yet been addressed.

Methods

Content analysis

Sample frame

We content-analysed a sample of TV programmes for 15 channels with the largest audience, including 6 national broadcast channels—Canal 13, Chilevisión, La Red, Mega, TVN and TV+—(60.3% of the audience at the time of the study’s planning),10 9 paid cable channels—A&E Mundo, AMC, AXN, Fox Channel, TNT, Cartoon Network, Discovery Kids, Disney Channel and Disney Junior. All programmes aired on each of 7 days on three randomly selected weeks (94 500 min of programming) between 11 March 2019 and 3 June 2019 were recorded during viewership peak times for youth aged 4–24 years (20:00 and 23:59 hours, prime time for adults and minors), plus from 00:00 to 00:59 hours (common among older youth), for a total of 5 hours per day.

Coding procedure

Following the methodology described by Lyons et al,11 TV programmes were divided into 1 min intervals and coded for tobacco occurrences, consisting of presentation or representation of a tobacco product or its consumption. Tobacco occurrences were parsed into five categories.

  • Explicit tobacco use: use of any tobacco product (cigarette, cigar, pipe, waterpipe or other (eg, chewing tobacco)) onscreen by a character. Electronic devices (eg, e-cigarettes) were coded as vaporisers, even if their tobacco content could not be ascertained. Occurrences in indoor places prohibited by the Chilean smoke-free law tobacco were coded as a violation of the smoke-free law.

  • Implied tobacco use: any inferred tobacco use occurring without actual use onscreen (eg, a comment about going for a cigarette or smoky atmosphere) and further coded as verbal or non-verbal.

  • Tobacco paraphernalia: the onscreen presence of unlit tobacco products or tobacco-related materials, coded by the type of appearance (including tobacco packs, matches, lighters, ashtrays or smoking area signs).

  • Tobacco brand appearance: the presence of clear and unambiguous tobacco branding, whether sold in Chile. It included branding visuals in tobacco packs, advertisements appearing within other programmes, branded merchandise and verbal references to such brands.

  • Other references to tobacco: any reference to tobacco that did not involve actual or implied use (eg, a news report of the economic performance of a tobacco company), coded as verbal or non-verbal.

Each 1 min interval was classified 0 or 1, depending on whether a tobacco occurrence was observed. Multiple occurrences of the same category in the same 1 min interval were considered a single occurrence. Occurrences that crossed a transition from 1 min interval to the next were recorded as two separate occurrences. Occurrences in different coding categories but the same interval were recorded as two separate occurrences. We coded partial minutes at the end of a programme interval as complete minutes if the programme content lasted >10 s.

Each minute interval was classified according to its valence into clearly and exclusively positive or not. A tobacco occurrence was considered positive when the observer concluded that it cast tobacco use, promotion or its industry in an attractive light or as inconsequential to health, the economy or the environment and was not mixed with other messages that could detract from this valence. Negative to tobacco intervals typically contained images of no smoking signs or characters diagnosed, sick or dying from diseases explicitly linked to tobacco use in the storyline.

The study considers four independent variables hypothesised to be associated with tobacco occurrence frequency and subject to regulation.

  • Programme genre: animated productions, non-animated feature films, non-animated series, reality shows, soap operas, news programmes—including documentaries—and others. The genre was identified from the programme announcement, the Internet Movie Database, the channel’s web page or the researcher’s discretion.

  • Type of channel: the 15 channels were classified as broadcast (6 channels) or pay channels, further classified into those targeting the general audience—5 channels—or children and youth—4 channels.

  • Programme production nationality: Chilean versus non-Chilean productions.

  • Protection of minors: the National Television Council of Chile requires TV channels to protect minors under 18 years from 06:00 to 22:00 hours from exposure to inappropriate content.12 It does not explicitly include tobacco-related content as inappropriate for minors. However, it has a general provision to prevent minors from being exposed to programming and advertising that could seriously damage their health and their physical and mental development. Additionally, the tobacco control law of 2013 bans any tobacco advertising and promotion, including on TV.13 We considered whether tobacco occurrences differ between the emission during and outside the protection of minors’ schedule during prime time and whether advertising during commercial breaks carried any tobacco advertising.

Coding implementation and reliability

A team of 10 trained observers coded each 1 min interval using a questionnaire (online supplemental file 1) on REDCap (V.9.7.5).13 14 Three members of the research team reviewed 10% of all observed minutes. The per cent agreement between the observer and the collegiate supervisors’ criteria on the five types of tobacco occurrences ranged from 98.1% for implicit use to 99.8% for branding.

Outcomes

Tobacco occurrences

When a 1 min interval contained any of the five types of tobacco occurrences, it was classified as having tobacco content. The number of total tobacco occurrences in the sample was calculated by summing all five tobacco occurrence types across all minutes. The hourly frequency is the number of occurrences divided by the total hours of programming and is presented by occurrence type.

Population exposure

Reach is the population exposure to tobacco imagery—a measure of the frequency of tobacco impressions seen by the audience aged 4–24 years. Reach was calculated by the type of occurrence, multiplying the number of tobacco occurrences in each 1 min interval by the estimated average number of people aged 4–24 years watching at that moment. Live audience viewing figures were collected and provided by Kantar IBOPE Media Chile from their peoples’ meter study (https://www.kantaribopemedia.cl/). Their sample represents the non-institutionalised people of 4+ years of age living for longer than 6 months in households with a TV of the most populated municipalities of Chile without consideration of their nationality. It represents a total of 7 702 676 individuals or approximately 40% of the Chilean population. The sample excludes households living in extreme poverty.

Analysis

Programming airtime was summed across all 15 TV channels, along with estimated hours of exposure to the 4–24 years demographic and persons of all ages. These metrics are also reported by channel and programme characteristics. The total number of tobacco occurrences and impressions received by the population of 4-year to 24-year olds during the observation period is reported, along with the average number of impressions viewed per hour, overall and by channel and programme characteristics.

Using multivariable weighted logistic regression, we assessed the odds of exposure to tobacco impressions among 4-year to 24-year olds as a function of channel and programme characteristics. The dependent variable was whether a 1 min interval contained a tobacco occurrence. Independent variables included the type of channel the interval was broadcast on (broadcast or pay), interval programme genre, whether the programme in that interval was produced in Chile and whether the interval was broadcast during the minor’s protection schedule. Type of channel and country of production were collinear because 99.9% of pay channel productions were non-Chilean, so the type of channel was dropped from the analysis. We ran four models; the four dependent variables were: any tobacco occurrence, explicit tobacco use, smoke-free violation and tobacco brand appearance. The regression used robust variance estimates to account for the clustering of tobacco occurrences within programme units, defined as self-contained content or narrative with a start and an end during the same day. The analysis was weighted to account for 4–24 viewership, so that the ORs reflect odds of exposure among 4-year to 24-year olds. ORs were considered statistically significant when the p value was <0.05. The analysis was conducted using STATA V.13.

Results

Media sample

About 2% of the minutes of broadcasting could not be observed either due to recording failure or low quality of the recording. A total of 92 639 of the planned 94 500 min were analysed. The recorded broadcasting comprised 74 833 complete and 6285 part-time minutes of 2020 programming units for a total of 81 118 1 min programming intervals. There were 10 722 of these intervals in which some publicity occupied part of the screen. The recorded broadcasting minutes comprised 11 521 min devoted entirely to advertisements. There was no pro-tobacco or anti-tobacco depictions in advertising.

Table 1 describes the programming airtime, duration of exposure of viewers of 4–24 years and all ages, by type of channel, the programme’s genre, the nationality of the production and the time of emission. Animated productions, feature films and series appeared 25.6%, 22.1% and 14.3% of the programming time, overwhelmingly non-Chilean productions. Chilean productions made up 29.7% of the programming time. Most were news programmes and other programmes, such as talk, music or humour shows, during 38.7% and 39.7% of Chilean productions’ airtime.

Table 1

Programming airtime, duration of exposure of viewers of 4–24 years and all ages, by type of channel, the programme’s genre, the nationality of the production and the time of emission, during the observation period

Tobacco occurrences

There were 2230 min intervals (2.7% of total programming) containing any tobacco occurrence in 386 (19.1%) of the programming units. Of these 2230 min intervals, 21.8% contained two tobacco occurrences and 5.3% more than two. Figure 1 depicts the distribution by type of occurrence. Explicit tobacco use was the largest category, comprising 52.1% of all minutes with tobacco impressions, followed by paraphernalia (39.9%) and implicit use (27.7%). About 16% of tobacco occurrences depicted violations of the smoke-free law. Brand appearances were relatively rare at only 5.2% of occurrences. Of the 1162 min intervals with explicit tobacco use occurrences, 781 (67.2%) portrayed cigarette use (763 only cigarettes and 18 cigarettes and other products). Cigars were portrayed in 296 (25.5%) min intervals with explicit use (273 only cigars and 23 cigars and other products).

Figure 1

Number of 1 min intervals with tobacco occurrences, by type. Note: The sum of occurrences by type does not add to 2230 because some of the minute intervals had more than one impression type.

Fifty-two (2.3%) of the intervals with at least one tobacco occurrence had a negative valence. Most of these intervals (75%) contained occurrences classified as ‘other’. None of the intervals with explicit use, smoke-free violations and branding occurrences had a negative valence.

Table 2 presents the total number of impressions received (reach) by the 4-year to 24-year olds during the 3 weeks of broadcast observed by type of impression, type of channel, the programme’s genre, the nationality of the production and the time of emission. During the observed period, young people received >29 million tobacco impressions, of which almost 11 million involved explicit use of tobacco (mean 8000 impressions per hour of programming). Youths saw almost 3 million smoke-free violation impressions (mean 2100 per hour of programming) and 1 million tobacco brand impressions (mean 800 per hour of programming).

Table 2

Tobacco impressions (in thousands) received by the population of 4-year to 24-year olds during the observation period by type of impression, type of channel, the programme’s genre, the nationality of the production and the time of emission

In a multivariable analysis, the adjusted ORs presented in table 3 indicate that the exposure to any tobacco, explicit tobacco use and smoke-free violation impressions were notably more likely in non-Chilean productions, particularly during the broadcasting of animated productions and feature films. Exposure to tobacco branding was associated only with watching feature films. Sparse data prevented some genres from being analysed in the regression models with smoke-free violations and tobacco branding as dependent variables. Also, production nationality was dropped from the regression model since all branding occurrences in news programmes were of Chilean production, while all branding occurrences in films were not.

Table 3

Variables associated with tobacco impressions received by people aged 4–24 years by type

Discussion

Exposure magnitude

Our results show considerable youth exposure to tobacco imagery in Chilean TV. Young people received millions of impressions during the observation period at hourly exposures in the tens of thousands. A relatively small number of tobacco occurrences within 2.7% of the total broadcast minutes is responsible for this large exposure. TV is, therefore, a powerful means of promoting tobacco use that presently is largely unregulated in Chile.

It is difficult to compare the magnitude of young people’s exposure in our study to other countries because of the paucity of comparable studies. We identified 22 studies that have analysed the tobacco imagery content of TV programmes.11 15–35 Of these, only four have measured the population’s exposure to TV tobacco imagery, mostly in specific programming genres, such as films or reality shows.11 33–35 Of these, only one has assessed the population’s exposure to tobacco imagery across all genres of regular programming.

This study11 indicates that in the UK, in 2010, 3.2% of the prime-time programming 1 min intervals on broadcast channels contained at least one tobacco occurrence, and 1.1% contained an explicit use occurrence. Branding occurrences were 0.1% of the programming time. The equivalent figures in Chilean broadcast channels were 1.6%, 0.8% and 0.1%. Therefore, the prevalence of tobacco occurrences in broadcast channels was slightly lower in Chile than in the UK, except for tobacco brand appearances.

These occurrences in the UK delivered 59 million of any type of tobacco impressions, 19 million of explicit use and 3 million brand impressions to people under 18 years of age.11 Although these figures are not strictly comparable to that of our study, primarily due to differences in the size of the studied exposed population, TV exposes young people to millions of tobacco impressions in both countries.

Source of exposure

The primary sources of young people’s exposure to tobacco impressions in Chile were feature films and animated productions, most (>99%) being non-Chilean productions. Whether films and animated productions are the primary sources of exposure in other countries’ TV broadcasting is challenging to discern because we did not find any comparable analysis to ascertain their role. Lyons et al11 reported that in the UK, tobacco content of any type and explicit use was significantly higher in films than in other genres, except reality shows. However, they did not relate the extent of the exposure from films among its viewership, even though they assumed it would be substantial.

Nevertheless, the importance of feature films as a source of TV exposure to tobacco imagery can be assessed considering that feature films are not made specifically for TV, and their tobacco content has been analysed when released for theatrical or other showings. The existing evidence shows that films are a critical source of tobacco imagery in the European36–38 and Latin American39–41 continents and countries like India,42 43 New Zealand,44 Nigeria45 and the USA.46–48 It is not surprising, therefore, that films are a means for delivering tobacco impressions when broadcast on TV. What is revealing is that in Chile, they play such a fundamental role in TV compared with other genres. Watching films on TV increases the odds of being exposed to any tobacco, explicit use and smoke-free violations by 4, 5 and 28 times, respectively, compared with watching a news programme, given the genre programming patterns in Chile.

A few studies have estimated the reach of movies to young audiences. In the UK, 572 movies delivered 1.09 billion tobacco impressions in theatres to youth 7–17 years between 2001 and 2006.49 In the USA, 534 movies delivered 13.9 billion tobacco impressions in all venues to youth 10–14 years of age since the film’s release till 2003.50 However, to compare the reach of movies in theatres and TV, we would need exposure rates by person/time for the same age groups, which are not available.

Animated production increased the odds of exposure to explicit use (5 times) and smoke-free violations (26 times) compared with news programmes, during the observation period and given the genre programming time patterns at the time in Chile. The role of cartoons as a primary source of TV tobacco impressions has not been documented so far. However, the G-rated animated feature films released in the USA during most of the 20th century have been documented as a source of tobacco imagery, although not as significant as non-animated feature films.51 52

In Chile, the pre-eminence of cartoons as a source of tobacco imagery seems to be driven by a single show: The Simpsons. Indeed, The Simpsons are featured as intended for adults, but children and youngsters watch this series frequently. In Chile, this series has been broadcast for several decades. Although at the beginning it was shown after midnight, it ended up being showed during the period when children are supposed to be protected,53 despite being very appealing to youth.54 The role of the Simpsons in Chile is not surprising as it has been documented as a prominent source of harmful messages,55 including tobacco imagery in several countries.28 33 56 57

The role of reality shows in exhibiting tobacco imagery appears to be different in Chile and the UK. While our analysis does not attribute any significant role to this genre as a source of exposure, Lyons pointed to reality shows as a notable source of tobacco occurrences in the UK, mainly tobacco branding. A possible explanation is that in Chile, 76.3% of the programming minutes of reality shows were Chilean productions and these are associated with less tobacco depiction.

Finally, although non-commercial tobacco branding occurrences are not frequent, they generate >1 million impressions among 4-year to 24-year olds. The odds of exposure to branding in films almost doubled that of news programmes. This finding indicates how the advertising ban in Chile might be circumvented.

Strengths and limitations

A significant limitation is that our results underestimate the real impact of tobacco appearance on the Chilean population during the prime time of the selected channels. The reason is that the audience data available from the Kantar Ibope People Meter survey extrapolates audience data to approximately only 40% of the Chilean population. Therefore, if the rest of the Chilean population were to have the same TV viewing patterns as in the People Meter sample, the number of impressions received by young people could double our estimates. Another possible limitation is that our TV programme sample is susceptible to seasonal influences on television content and news stories. However, it is unlikely that this has distorted our findings because the primary sources of tobacco content were programmes that are shown throughout the year. Finally, our analysis does not include the exposure to tobacco imagery on streaming platforms, the internet and other entertainment venues.

The study’s strength is that it analysed considerably more broadcasting time than any other published study. The median of the minutes sampled in existing content analysis TV studies is 6825.0 (IQR 4072.3–9498.0), with the maximum sample standing at 27 083 min28 compared with our sample of 92 639 min.

Conclusions

In conclusion, our study points to the need to protect youth from tobacco imagery on TV. To this end, new legislation should prohibit depicting identifiable tobacco brands or images in any TV programme content. Additionally, it should prescribe strong anti-tobacco advertisements at the beginning of any TV programme that depicts tobacco content. We also recommend implementing a mechanism requiring a no-pay-off certification to depict tobacco imagery of any type in a TV programme as suggested by the implementation guidelines of article 13 of the WHO FCTC, to which Chile is a party. Finally, to discourage tobacco imagery in Chilean productions, Chilean media productions with tobacco imagery should be ineligible for public subsidies. Policies favouring media producers, whether for cultural conservation or commercial competition, should be harmonised with the fundamental public health imperative to protect the public’s health from tobacco promotion.

What this paper adds

  • Exposure to audiovisual tobacco content in films is a risk factor for smoking in young people; however, few studies have measured young people’s exposure to TV tobacco imagery, and none has assessed this exposure across all genres of regular programming of both broadcast and paid channels, as we do in this study.

  • Our study reveals that, in Chile, prime-time television broadcast a relatively small number of tobacco occurrences but delivered millions of tobacco impressions to 4-year to 24-year olds during the observation period with hourly exposures in the tens of thousands.

  • The study confirms that feature films are a significant source of this exposure as are in other media, but reveals that animated productions theoretically geared towards adults, are a substantial source in TV.

  • Exposure to tobacco imagery came almost entirely from non-Chilean produced programmes.

  • Although commercial breaks did not contain any tobacco advertising, young people watching TV were exposed to tobacco brand impressions from regular TV programming, effectively circumventing the advertising ban in Chile.

  • Our study calls into question the efficacy of the few existing regulations related to tobacco imagery on TV in Chile.

Abstract translation

This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Data availability statement

Data are available on reasonable request. Data are available on request from the Centro de Epidemiología y Políticas de Salud of the Universidad del Desarrollo 3 years after the end of data collection (June 2019).

Ethics statements

Patient consent for publication

Ethics approval

The Scientific Ethical Committee of the Bioethics Centre of the University del Desarrollo in Chile provided ethical clearance to this study.

Acknowledgments

The study team acknowledges the support from Kantar IBOPE Media Chile, who provided the TV viewing data from Chile. The team also thanks Dr Leonardo Cabrera and the Centre for Biomedical Informatics of the UDD for the programming of the REDCap questionnaire.

References

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Footnotes

  • Twitter @armi0156, @ximenaguilera

  • Contributors AP designed the study. AP and JS led the writing of the manuscript. OU, XM, CC and IM supervised the survey design and implementation and contributed to data analysis and writing of the manuscript. ID and IM undertook the data analysis and contributed to the preparation of the manuscript. MH, AO, CG and XM contributed to the writing of the manuscript. All authors contributed to the revision of the manuscript.

  • Funding The National Research and Development Agency of Chile (ANID) funded this research under grant #SA18I0024.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.