The horrific Manchester terror attack raises uncomfortable questions about the imperfect integration of Britain’s Muslim minority.

A series of such brutal incidents in the United Kingdom involved native-born British subjects, not recent refugees. And despite some fears of Islam’s surging influence, the most recent numbers show that self-identified Muslims still comprise only 5 percent of the UK population. The far more worrisome numbers involve the declining percentage who say they are Christian–down from 72 percent to 59 percent today.

By far the fastest growing religious group in Britain, as in the United States, are those who say they have “no religion”–now 25 percent of Brits, but only 15 percent in 2001.

Those who hope that America and the United Kingdom will maintain their distinctive cultural identities are right to worry about Christianity’s declining numbers. But we should remember that those losses reflect disenchantment and disaffiliation far more than the growth of Islam or any other rival faith.