When the Institute for Jewish Policy Research launched its report on marriage this week , there was surprise among the audience.

Although the intermarriage rate, at 26 per cent, has reached an all-time in the UK, many had expected it to be higher. If it has not quite plateaued, it has risen only slightly in the past couple of decades.

There has been an assumption that where American Jewry goes, British Jewry eventually follows. So if the American intermarriage rate has stood at over 50 per cent for some time, it led to the belief that the UK would not be so far off now. (Important differences remain between the two communities, however: British Jewry is more Orthodox and traditional and has a much higher proportion of Charedim).

Whatever the figures, in the established way of thinking intermarriage has always been regarded as a threat to Jewish continuity. But given the high rates in America, an alternative view has been suggested; that intermarriage can actually increase the Jewish population.

As Dr David Graham, author of the JPR report, explained it, here is the argument put by the intermarriage optimists. Let’s assume that an average couple has two children. If you have four Jews, you have two Jewish couples who produce, between them, four Jewish children.

If, however, those four Jews each were to marry someone outside the community, there would be four couples with eight children. Now if more than half those children are raised Jewish, say six out of eight, then you have increased the Jewish population.

The only problem is that current evidence suggests this is wishful thinking – and JPR’s own statistics rather explode any rose-tinted scenario. Fewer than one in three children of intermarried couples in the UK are raised Jewish, whereas almost all those of Jewish couples are.

But you could take a different line. Given the widely pejorative attitude towards intermarriage, that discourages people from identifying with the Jewish community. So if we adopted more of an open-door policy, some would argue, then maybe more intermarried couples would be prepared to bring their children into the community.

The decision of the Reform movement last summer to recognise the children of Jewish fathers was a step towards greater inclusiveness. It remains to be seen whether it will result in a larger number of children from intermarried families identifying as Jewish.

Another question raised by the JPR report is what lies behind the relative stabilisation of the intermarriage rate. Some will suggest that it must be the effect of greater investment in Jewish youth and education – the result of the “continuity agenda” in the early 1990s.

But JPR argues that the rate had already steadied by that time, so there is no clear evidence yet of any direct benefit of enhanced education, including Jewish schooling.

To read the JPR report, go here.