We present a general, physically motivated non-linear and non-local advection
equation in which the diffusion of interacting random walkers competes with a
local drift arising from a kind of peer pressure. We show, using a mapping to
an integrable dynamical system, that on varying a parameter, the steady state
behaviour undergoes a transition from the standard diffusive behavior to a
localized stationary state characterized by a tailed distribution. Finally, we
show that recent empirical laws on economic growth can be explained as a
collective phenomenon due to peer pressure interaction.Comment: RevTex: 4 pages + 3 eps-figures. Minor Revision and figure 3
replaced. To appear in Phys. Rev. Letter