The counting of Jews has never been straightforward. Orthodox Jews maintain that it is forbidden to count Jews directly. Some say that in biblical times a half-shekel was taken from every Jew, and then the coins were counted.
Today, in Israel, the prohibition on counting Jews is side-stepped through the argument that the census also counts non-Jews. In Britain, the census now contains a religious identity question, but I have come across individual Jews who tell me either that they do not answer this question, or that they answer in a nonsensical manner.
In Britain the counting of Jews has other pitfalls. Any semblance of Anglo-Jewish communal planning must have, as its starting point, an estimation of the numbers of Jews for whose benefit plans are being drawn up. Over the decades, social scientists and demographers have devised a variety of methodologies to assist in arriving at such approximations.
Some have used burial statistics as their starting point. Others have utilised marriage figures, and even records of circumcisions, which are then refined mathematically using national ratios of male-to-female births.
When I started polling Jewish voters, my early samples were based upon mezuzah counts. The samples I derived proved remarkably accurate when I was later able to compare them with the lists of Jewish voters kept by local political parties.
Of course, not every Jewish-occupied dwelling boasts a mezuzah on its front-door. Not every Jewish male is circumcised. Not every Jewish couple goes through a religious marriage ceremony. There is compelling evidence that many Jewish couples are delaying formal synagogue membership, certainly until children are born.
Then we are faced with the problem of what constitutes a synagogue. In the Charedi world, many places of worship are completely lacking in formal membership structures - numerous prayer-houses being owned and maintained by private individuals or self-perpetuating trusts. And finally we are faced with the ultimate question - with which I do not propose to deal here - "who is a Jew?"
So the counting of Jews, and specifically of British Jews, is full of unavoidable potholes. But it has also acquired an unsavoury political dimension.
Currently, the acknowledged authorities on the counting of British Jews are Daniel Vulkan, research officer at the Board of Deputies, and Dr David Graham, director of social and demographic research at Jewish Policy Research (JPR). Their computations are internationally accepted by internationally recognised expert demographers and demographic statisticians.
Last month, Dr Graham and Mr Vulkan published their latest findings on synagogue membership in the UK. After painstaking research (which included special attention to the conceptual challenges associated with synagogue affiliation among Charedi Jews), they concluded that the decline in synagogue membership in the UK appears to have all but ceased, thanks largely to the growth of Charedi communities but that, while the Charedim have more than doubled their membership share over the past two decades, the non-Orthodox share has also increased.
According to Vulkan and Graham, the Charedi share of total synagogue membership is now 10.9 per cent, and the non-Orthodox, 30.8 per cent, while the "central Orthodox" share has declined over the same 20-year period from 66 per cent to 55 per cent.
These findings have come under predictable but nonetheless astonishing attack from the religious right.
Dr Yaakov Wise, author of a PhD thesis on ultra-Orthodoxy in Manchester, insists that reliance upon synagogue membership figures alone produces "a grossly distorted picture."
According to Dr Wise (whose CV indicates no expertise whatever in demography but plenty of experience in marketing), Charedim now actually constitute between 18 and 20 per cent of Anglo-Jewry, and the Progressives only 17 per cent. And from Rabbi Avrohom Pinter has come the shocking claim that, in publishing the findings of Graham and Vulkan, JPR was simply pursuing "an agenda" grounded - he alleges - in its "discredited track record in trying to delegitimise the position of the Chief Rabbi and artificially boost the position of the Progressives."
These are serious charges, touching as they do upon the professional reputations of two acknowledged authorities in the field of Jewish demography, and upon the public standing of JPR.
No doubt Dr Wise and Rabbi Pinter will make public the evidence upon which their allegations are based.