DellaPergola estimates that of the present 13 million Jewish population, 2 million have a "normative/traditional" identity who "nearly exclusively adhere to a self-contained complex of Jewish beliefs, norms and values, and who consistently perform Jewish traditional ritual practices.

A further 6 million have an "ethnic-communal" type identity, which includes those whose main attachment to Judaism is through membership in a religious congregation. Here, as in the case of some contemporary non-Orthodox congregations, the sense of community is preserved, while the unique element of Jewish traditional or cultural exclusiveness is not. About half this group lives in the Diaspora, particularly in Latin America, Britain and the USA. The other half lives in Israel and blends a national Israeli identity with some elements of traditionalism.

The third type of Jewish identity, the "cultural residue" type, includes those for whom some attachment to Judaism may persist independently of clearly recognisable personal religious behaviour or involvement in a Jewish community. About 4 million are estimated to hold this private and non-involved Jewish identity, particularly in East and Western Europe and the USA.

The fourth type of Jewish identity is that of the "zero Jewish" or "dual Jewish/non-Jewish" Jew, which is applied to people of Jewish origin whose cultural outlook and frame of reference are in DellaPergolaÕs words "basically non-Jewish", but who nevertheless belong within the definitional framework adopted to quantify the Jewish population. It is in this fourth type that Messianic Jews would normally be included, and points to the value of the core/periphery distinction that is being made. (4)