Five such concepts were time dependence, positional movement, share movement, nondirectional income movement, and directional income movement. I then went on tO consider what these different mobility concepts would produce in certain simple examples. Only when everyone's income stays 31. In other cases they give different answers because they are measuring in light of fundamentally different concepts. The next section compared measures arid axioms.
Ok indices are measures of income movement.
I also considered several possible axioms for income mobility, including axioms for normalization, level insensitivity, relativity, strong relativity, and trans- lation invariance and showed that different mobility measures satisfy these different axioms. The results of this chapter show that how mobility is conceived and how it is measured make an important difference. References Atkinson, Anthony B., Franc,ois Bourguignon, and Christian Morrisson. Empirical Studies of Earnings Mobility. Bartholomew, David T. 1982.