The first three Natsal surveys, which includes Natsal-3, didn’t ask participants about their gender or sex (as assigned at birth); rather the interviewer recorded whether the participant was female or male based on certain details. For example, the interviewer concluded whether a person was female or male based on their outward appearance (e.g. their clothing) and their name.

These observations were then used to make assumptions about the participant’s sexual anatomy for the rest of the interview. However, this approach is limiting and results in some misclassification, which needs to be considered when interpreting data from earlier rounds of Natsal.

In contrast, the next Natsal survey (i.e., Natsal-4) will ask participants about both their sex as assigned at birth and their gender, because a person’s assigned sex doesn’t always align with their gender.  For example, some participants will be transgender including those who are non-binary (i.e., a person who does not identify with a rigid female/male binary).

The wording of some Natsal questions and the response options offered to participants may seem a little out of date. However, it’s very important that the questions asked in Natsal can be used to measure change over time in behaviours and attitudes.

In order to do this, the questions need to be worded in the exact same way in each survey, so that the resulting data can accurately be compared ‘like for like’. Other steps to help achieve this include presenting response options in the same order and asking the question in the same part of the interview, in the interviewer-administered part rather than in the self-completion sections (or vice versa).

For other questions, Natsal endeavours to make sure that the wording used is the most relevant for the times. For example, Natsal-1 and Natsal-2 asked participants ‘Have you ever attended a sexually transmitted disease (STD) or special venereal disease (VD) clinic?’ but for Natsal-3 the question instead referred to ‘sexual health clinics’, which is the more common name for these health services nowadays.

This is one of the most common questions that Natsal researchers get asked. The simple answer is that we don’t know whether or not participants are telling the truth, and so that’s why the data should really be described in terms of reported behaviours and attitudes.

However, the researchers put a lot of effort into creating an environment that encourages participants to answer the Natsal questions honestly and accurately. For example, the very first letter that is sent to randomly-selected addresses introduces Natsal and highlights its importance as a scientific study. This letter also describes the important impacts Natsal has had for policy and practice.

The formal language used in the actual interview, and the use of showcards and self-completion modules to increase privacy are also used to increase participants’ willingness to report ‘the truth’. However, there are still inconsistencies in the Natsal data, possibly reflecting how some people might choose to ‘massage the truth’ often for genuine reasons including difficulties in remembering details, and also because the response options Natsal offers don’t always ‘work’ for everyone as sex lives are sometimes complicated.

Natsal is limited by the number of questions it can ask as the survey is designed to take around 50 minutes on average to complete. It is designed this way so as not to be too burdensome for participants. Although that may sound like a long time to be answering questions about sex and sexual health, Natsal also needs to ask questions that help to contextualise the information it gathers on sex and sexual health.

For example, sociodemographic questions including age, ethnic group, educational attainment, and so on. Plus, the concept of sexual health has evolved to be far broader than simply about ‘bugs and babies’ and now includes sexual function, sexual pleasure, and sexual violence, as part of a broader understanding of sexual wellbeing. Natsal’s remit has therefore considerably widened from the very first survey that focused on understanding HIV risk to needing to address a much broader range of topics.

It is important therefore that Natsal researchers consult and listen to its stakeholders – that is, the people who will be using the resulting data – to decide upon the most important questions that Natsal needs to ask in order to collect the most useful data to inform policy and practice.

To consent to sexual activity means to freely agreeing (with full capacity) to engage in any sexual activity. This means that a person has to be able to agree to sexual activity with full understanding of what they are agreeing to, and they must be under no pressure to say ‘yes’. When a person has not agreed then this is non-consensual sex.

In the self-completion section of Natsal-3, participants were asked: “Has anyone tried to make you have sex with them, against your will?” If a participant responded “yes” then they were then asked whether this then occurred.

The term ‘non-volitional sex’ is used as the most literal translation of the question asked in Natsal-3. Irrespective of the degree of coercion or force used, it still represents a violation of sexual autonomy and is therefore a form of sexual violence.