Integration affects economic growth mainly through two different Channels: The scale-effect channel and the factor-reallocation channel. Explain it

In order to investigate both channels within a unifying framework, we employ a simple descriptive growth model. The scale-effect channel increases either the long-run growth rate or the level of the balanced growth path. The factor-reallocation channel is ambiguous. It is shown under which conditions this mechanism induces either a rise or a fall in the long-run growth rate. In addition, a number of policy conclusions are drawn.

"scale-effect channel” relies on positive spill-over effects and increases the growth rate of the integrated economic area either permanently or temporarily.  "factor-reallocation channel" affects the share of resources allocated to the dynamic sector(s) of the economy and hence changes the growth rate.