IB Psychology HLTopic 1 — Health ProblemsPaper 1 & 2Core skill~9 min read
How Common Is Smoking?
Smoking is one of the few health problems where the global numbers are genuinely improving. That makes it a useful case study, because you get to explain a falling trend rather than a rising one — and explaining why it is falling turns out to be much harder than measuring it.
📘 What you need to know
Prevalence is how common a behaviour is in a specific population over a given time. It can be a percentage or cases per 10,000 or 100,000.
Three types: point prevalence (right now), period prevalence (any time in a set window, e.g. the past 12 months) and lifetime prevalence (ever).
WHO data: in 2022, around 20.9% of the world’s population aged 15 and over smoked cigarettes.
Around 80% of the world’s 1.25 billion tobacco users live in low- and middle-income countries.
Global prevalence is falling each year, though some countries show rising rates among men.
Gender gap: in 2022 about 34.4% of men and 7.4% of women used tobacco, and the ratio has widened over time.
Valente et al. (2005): popular students were about five times more likely to smoke than average students.
Three ways to report prevalence
Type
What it counts
Why it matters
Point prevalence
The proportion smoking at one specific moment
Best for a snapshot, but misses occasional smokers
Period prevalence
The proportion who smoked at any time during a set window
Catches people who quit and relapsed within the year
Lifetime prevalence
The proportion who have ever smoked
Always the highest number, and the least useful for current policy
If a statistic in an exam looks surprisingly high or low, check which type of prevalence it is. The same population can produce three very different figures without anybody lying.
The global trend
The gap between the blue and red lines is the gender gap, and it is projected to keep widening in relative terms — from men being about three times more likely to smoke in 2000 to around five times by 2030.
Who smokes: age and gender
Gender. In 2000 men were roughly three times more likely to smoke than women. By 2022 it was around four times, and projections point to five times by 2030. The female decline is faster, but it started from a much lower base.
Region matters. South-East Asia had the highest female prevalence in 2000 at around 33%, down to about 10% by 2022. Europe now has the highest female prevalence at roughly 18%, and its decline is slower than Asia’s.
Age. Prevalence is around 13% in the 15–23 group, peaks in middle age at roughly 18–28% for 45–54 year olds, and falls again in the oldest groups.
The fall in later life partly reflects people quitting for health reasons, and partly reflects the fact that long-term smokers do not all survive to old age.
Research support: Valente et al. (2005)
Aim: to investigate whether popular students are more likely to start smoking.
Participants: 1,486 students aged 12–14 from 16 middle schools in southern California.
Procedure: three surveys. A baseline survey measured gender, ethnicity, age, grades, susceptibility to smoking and current smoking. A second survey two months later mapped social networks. A third followed up a year later. Popularity was operationalised as the number of times a student was named as a friend by others; smoking as having ever puffed or smoked a cigarette; susceptibility as refusing to commit to never smoking.
Results: popular students were about five times more likely to smoke than average students. Unpopular or isolated students were also more likely to be susceptible or to have already started.
Conclusion: popular students shape social norms. When they smoke, peers read it as acceptable or desirable, and because they are more connected, that influence spreads further.
The U-shape nobody mentions. Both the most popular and the most isolated students were at higher risk. That means two different mechanisms are running — status-seeking at one end and loneliness at the other — and any prevention campaign aimed only at “peer pressure” will miss half the problem.
Evaluation
Strengths
Vital public health information. Nicotine addiction carries serious health risks, so knowing where prevalence is concentrated directs resources.
Valente’s design tracked real networks over a year, which is far stronger than a one-off questionnaire about friends.
It points to early intervention. The study identifies adolescence as the window where smoking careers begin.
Limitations
Descriptive, not explanatory. Prevalence figures show what is happening, never why. Qualitative research is needed for the cultural and psychological reasons.
Cause and effect cannot be established. Health campaigns and falling rates go together, but there is no way to prove one produced the other.
Self-report of a stigmatised behaviour. Adolescents may under-report smoking, or over-report it to look grown up.
One region, one age band. 16 schools in southern California is a narrow base for a claim about adolescents generally.
Projections are not data. Everything past 2020 on the graph is a model, and models can be wrong.
EXAM QUESTION
Discuss the prevalence of one health problem. [22]
Step 1: define prevalence and name all three typesPoint, period, lifetime, with a one-line difference each.Step 2: give the global picture with real figures20.9% of over-15s in 2022; 80% of 1.25 billion users in low- and middle-income countries; falling trend.Step 3: break it down by gender and age34.4% of men vs 7.4% of women; peak in middle age; widening ratio.Step 4: use Valente, then evaluatePopularity effect and the isolated-student finding. Then self-report bias, one region, descriptive-only data.End on causality: the numbers show the change, not the reason for it
Link to concepts
Change
Smoking prevalence falls with age, which may reflect health problems developing, or starting a family and not wanting to expose children to smoke. At a societal level, smoking bans and rising awareness of the risks are plausible reasons for the overall decline. Plausible — not proven.
Causality
This is the honest limit of prevalence research. You can point to a relationship between health campaigns and falling rates, but you cannot isolate the campaign from everything else that changed at the same time: price rises, bans, social attitudes, and the arrival of alternative products.
💡 Exam tip
Learn two or three exact figures with their years. Precision separates a top answer from a vague one.
Explain how Valente operationalised popularity and smoking. Definitions matter and examiners reward that detail.
Use the isolated-student finding. Almost every answer mentions only the popular students.
Distinguish estimates from projections when discussing the graph.
The gender gap works for both the prevalence question and the culture question, so learn it once and use it twice.
“Descriptive, not explanatory” is the sentence that unlocks the evaluation on any prevalence question.
⚠ Common mix-up
Quoting a lifetime prevalence figure as if it were current smoking. Very different numbers.
Saying female smoking is rising. It is falling, and faster than male smoking in relative terms.
Assuming the gap widening means women are doing worse. It widens because women’s rates are dropping from a lower base.
Calling Valente an experiment. It is a survey-based longitudinal study.
Treating “ever puffed a cigarette” as regular smoking. That was the operational definition, and it inflates the count.
Presenting projections as facts. Everything after 2020 on the graph is modelled.
Up next: Why Obesity Rates Differ Between Cultures — we take the prevalence tools from these two pages and start asking what actually explains the differences.
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