Calculate the open economy multiplier with proportional taxes, T = tY, instead of lump-sum taxes as assumed in the text.
The open economy multiplier with proportional taxes will be
Y = C + c (1 - t) Y + I + G + X - M – mY
Y - c (1 - t) Y + mY = C + I +G + X – M
Y [1 - c (1 - t) +m] = C + I + G + X – M
Y = C + I + G + X – M / 1 - c (1 - t) +m
Autonomous expenditure (A) = C + I + G + X – M .Therefore, open economy multiplier with proportional taxes will be –
Y = A / 1 - c (1 - t) +m
∆Y/∆A = 1 / 1 - c (1 - t) +m