A new study of Orthodox Christians in America has found a larger-than-expected number of converts, mostly from Roman Catholic and evangelical Protestant backgrounds.In practices and doctrines, Roman Catholicism is very similar to the Orthodox Church, so converts to the Orthodox Church from the Roman Catholic Church are retaining much of their religious capital when switching. The switch from evangelical Protestantism involves a bigger change, but that change is probably more in ritual and practice than in doctrine.
Notice who is not mentioned as converting. Converts into the Orthodox Church, which is a Christian denomination, are coming from other Christian denominations--not from Buddhism, not from Islam, not from Hinduism, etc. Here's our religious capital theory in action.