The next census takes place on 21 March. As in 2001 and 2011, it will include an optional question about religion with a ‘Jewish’ response option. Please tick it.

It will take you barely a second. All it involves is putting a tick in a box. But it is one of the most important and consequential things you can do to contribute to the future of British Jewish life.

The national Census takes place once a decade. Every household in the country is legally obligated to complete it, so it always generates the most complete and detailed set of data imaginable. Conducted in England and Wales by the Office for National Statistics, it provides essential data to support planning in every walk of life, including health, education, housing, employment, economics, social inclusion and political representation. There is not a single issue happening in Britain today that cannot be better understood in some way by referring to census data.

In 2001, the census included a question on religion for the first time. It simply asked: ‘What is your religion?’ and offered several response options: Christian, Buddhist, Hindu, Jewish, Muslim, Sikh, Other or None. It was controversial at the time – the government needed better data to understand increasingly multicultural Britain, but there were concerns that people might find the question too intrusive. In the end they decided to include it, but, uniquely among all questions asked, to make it optional.

266,740 people ticked the ‘Jewish’ box. Because the question was optional, that figure did not capture the total size of the Jewish population. But it came close. Using other techniques, the UK Jewish population was estimated at 300,000 at the time, so the census picked up about 90% of the whole. A very similar result – 271,259 people – was obtained when the question was repeated in the next census in 2011.

For most Jews, discussion about the census ends here. They think that Jewish interest in it is limited to knowing how many people ticked the box. But they could not be more wrong.

Close examination of census data allows us to construct an immensely detailed portrait of the Jewish population – its age profile, geographical contours, socioeconomic conditions, health status, living circumstances and much more. And the existence of these data helps every single Jewish organisation in the country to understand exactly what the Jewish population of the UK looks like, how it has changed over time, and how it is likely to evolve in the future.

Jewish Care has used the census to project how many elderly care places will be needed in care homes going forward. Partnerships for Jewish Schools (PaJeS) has used it to determine how many school places to provide. Langdon has used it to assess how many Jewish children have learning disabilities. World Jewish Relief has used it to build support for its work overseas.

It’s been used to help understand the scale and nature of antisemitism, to determine intermarriage rates and to help create low-cost housing for disadvantaged Jewish families. It’s used in every reliable survey of the Jewish population – every credible figure you have seen about the proportion of Jews who think x, do y, or believe z draws on census data.

Every synagogue movement, Jewish school, Jewish charity and foundation uses census data in countless ways, even if they don’t realise it. I know, because I spend much of my professional life sharing it with them, using it to explain the Jewish population dynamics they need to understand to determine how best to serve our community.

The next census takes place on 21 March. As in 2001 and 2011, it will include an optional question about religion with a ‘Jewish’ response option. Please tick it. Indeed, please encourage every single Jew you know to tick it. That very simple task is one of the most consequential things you can do to help Jewish charities serve you and your family’s interests for the foreseeable future.

Dr Jonathan Boyd is Executive Director of the Institute for Jewish Policy Research, and independent research institute providing data to support Jewish organisations across Europe to help plan for the future. www.jpr.org.uk.