# Minimum Legal Drinking Age and Public Health in the UK - discussion

Luke Wilson, Fabrice Etilé

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## To cite this version:

Luke Wilson, Fabrice Etilé. Minimum Legal Drinking Age and Public Health in the UK - discussion. EuHEA PhD/Supervisor Conference, European Health Economics (EUHEA). FRA., Sep 2016, Barcelone, Spain. 10 p. hal-01605039

HAL Id: hal-01605039

https://hal.science/hal-01605039v1

Submitted on 5 Jun 2020

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Minimum Legal Drinking Age
and
Public Health in the United Kingdom

Luke Wilson (Lancaster U.)

Discussion by Fabrice Etilé
(Paris School of Economics)
# This research

* Main question: what is the causal impact of the MLDA of 18 on the drinking behaviour of young adults in UK?

* Design:

- the MLDA is considered as a treatment, with assignment depending on age in month. Cutoff=18 years-old.

- Regression Discontinuity analysis around the cut-off, i.e. compare those slightly younger than 18 to those aged 18 and slightly older.
# General comments

* Focus on an important policy issue.

* Nice contribution to the literature:

- Few existing studies for Europe.

- Easily replicable design (already validated in Carpenter & Dobkin, AEJ, 2009).

* First step to provide IV estimates of the impact of alcohol use on health outcomes.

* Overall writing is fine, though incomplete and imprecise at some places (polish/edit).
## Specific comments & suggestions

* Discuss more thoroughly threats to internal validity (Imbens & Lemieux, 2010):

- Identifying assumption is that the age at date of interview is independent from birthday: *test that the density of age is continuous around the cut-off* (manipulation is unlikely but who knows).

- *Not clear to me that all outcomes relate to « last week ».*

* If they measure average behaviours over the previous 12-months, then outcomes for the treated they are likely to reflect a mix of treatment and non-treatment
# Specific comments & suggestions

* Discuss more thoroughly threats to internal validity (Imbens & Lemieux, 2010):

- *Peer effects are likely to matter:*

* SUTVA (Stable Unit Treatment Value) is unlikely to hold, as the older in a cohort are likely to purchase for the younger => estimated effects underestimate the actual policy effect?

* In Section 5.4., you separate the « younger » of each school cohort from the « older » (born at the beginning of the academic year) : *find larger effects for the younger*.

* Standard errors?
Specific comments & suggestions

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# Specific comments & suggestions

* Econometrics: **convince the reader that your results are robust**

- Confidence bands on the RD graphs?

- Investigate and report the sensitivity of the results to:

* Inclusion of higher-order polynomial terms for age (cubic).

* Local linear regression approach to the estimation of the age function (less parametric, *rdrobust* command in Stata).

* (Report results for bandwidths of varying size).

- Placebo tests: change the cutoff – report the corresponding results
# Specific comments & suggestions

* Heterogeneity (discussion).

- The estimated effect is an ATE for a population that may be very heterogeneous in terms of Marginal Treatment Effect: it may be the case that some teenagers only are impacted by the MLDA.

* Sub-regressions by SES? Region?

* Other sub-samples of interest: personality traits, ...

- The effect of MLDA may have changed over time:

* Change in UK alcohol regulation: after 2003, 24-hours sales were allowed in bars and stores (?); real enforcement of illegal purchases by under-MLDA teens?
**Specific comments & suggestions**

* In your discussion, you may clarify the limitations of the study in terms of « external validity »:

- Alternative policies would be increasing the MLDA to 20 years-old (say), not to 18 yrs 1 month. So, ‘marginal’ ATE only?

- In Section 4, you very honestly discuss the possibility that other important events may occur at age 18 and around, like a relaxing of parental supervision; is it possible to investigate this issue (BHPS for this?).
**Specific comments & suggestions**

* In your discussion, you may clarify the limitations of the study in terms of « external validity »:

- This raises more generally questions regarding the mechanisms: does MLDA have an effect by effectively **restricting access** to alcohol? Through peer pressure (**social interactions**)？ Through internalized norms (**self-image/self-categorization effects**)？ Is it possible to disentangle these various channels?