The poor are finding it even tougher to escape from the lowest income ranks these days.

Most of those in the poorest income quintile spent all or nearly all of the period between 1996 and 2006 stuck in place, according to a new report issued by the Federal Reserve Bank of Boston. Those who did advance didn't move far.

The research, conducted by senior economist Katharine Bradbury, shows that economic mobility has also slowed in recent decades.