Maybe I am naive, but if g is the growth rate of an economy, and r the growth rate of a smaller part of it, doesn't this mean that if r>g the portion of capital growing at rate r increases? This would also mean that g increases.
r can be positive and g negative at the same time. Total growth consists of labour and capital growth. Piketty's point is that capital is growing faster than labour – if that continues forlong enough, we can end up in a world where 99% of income goes to owners of capital.
