Since publishing the JPR/Board of Deputies report on synagogue membership last month, I have been asked many questions about its findings.

Is the problem that young adults aren’t joining synagogues until much later than they used to? Is it that religious conservatism is preventing synagogues from evolving into attractive modern institutions? Is the British Jewish community destined to become a “tale of two cities”, based only in London and Manchester?

These are all good questions. But underpinning them are three deeper questions, all of which, I believe, ought to find their way on to the agenda of the community.

First: is Jewish belonging as a whole in decline, or are patterns of belonging simply changing? The report finds a decline of 20 per cent in synagogue membership since 1990, caused partly by demography, partly by disengagement. However, we also know that there are many other ways in which people can “belong” to the Jewish community that are not captured by the report’s findings. People can be members of Jewish organisations other than synagogues, or attend a synagogue regularly without being a member. They can be strongly committed to an alternative or “pop-up” minyan that doesn’t have a formal membership scheme, or they can feel a close affinity to a synagogue without ever paying membership dues.

These nuances need to be investigated to understand more precisely what the problem is that needs to be addressed. Is it that Jews are disaffiliating in greater numbers and proportions, or that our preferences for how we affiliate are changing? The answer will help us to direct our energies best: towards making synagogue membership a more compelling proposition, and/or towards developing a more multi-faceted approach to Jewish belonging that incorporates more innovative modes and models.

Second: what are the costs and benefits of the denominational shifts that are occurring? In 1990, there were about 17 centrist Orthodox and six non-Orthodox households to every one Strictly Orthodox household. Today those ratios are about four to one and three to one. The Strictly Orthodox share has climbed from 4.5 per cent of synagogue membership households in 1990 to 13.5 per cent.

That growth has been driven almost entirely by demography — specifically, very high birth rates and normal mortality rates within that part of the community. At the same time, membership of centrist Orthodox synagogues has fallen from two-thirds of all synagogue members to just over a half during the same period. In short, the balance between “moderate” and “strict” Orthodoxy is shifting in an increasingly conservative direction.

Whether that is good or bad is a matter of perspective. But it has implications, perhaps particularly in the realm of intra-Jewish relations, co-operation and co-ordination. The collective communal agenda item should be clear: what needs to be done now to ensure that intra-Jewish relations become a source of inspiration and enlightenment, rather than descending into internecine conflict?

Third: how should we manage a more geographically concentrated community? For the past 150 years, British Jewry has been consistently split two-thirds in London, one-third outside. But the balance is now shifting towards London. Indeed, almost half of all synagogue members in the UK belong to shuls in just four boroughs, in or around London: Barnet, Westminster, Hertsmere and Redbridge. Only about a quarter belong to synagogues outside London and its surroundings, and that proportion is falling over time.

Concentration is happening even outside London. With a handful of exceptions, notably Manchester and Gateshead, the majority of regional communities are in decline. Greater geographical concentration means fewer non-Jews will ever meet Jews, and fewer parts of the UK will be touched by the contributions to civil society Jews living there can make. In that context, the potential for Jews to be seen as stereotypes is only likely to grow, with all the perils that entails. We must work out how we can contribute to British society across the country, particularly in areas where Jewish populations are smallest.

So the data point to the risks: less community engagement, greater cross-communal tensions, and lower levels of understanding in wider society about who Jews really are. The challenge now is to ask the right questions that can lead the way towards wise communal policy.

Jonathan Boyd is Executive Director of the Institute for Jewish Policy Research (JPR)