MPC, MPS, + Multipliers

Spending Multiplier Effect→an initial change in spending (C, Ig, G, Xn) that causes a larger change in aggregate spending, or AD 
-multiplier=△ in AD/△ in spending
-multiplier=△ AD/△ C, I, G, or X
-why does it happen? → expenditures and income flow continuously which sets off a spending ↑ in economy

Calculating the Spending Multiplier
-spending multiplier can be calculated from MPC or MPS
-multiplier=1/(1-MPC) or 1/MPS
-multipliers are (+) when there's an ↑ in spending and (-) when there's a ↓ in spending

Calculating the Tax Multiplier
-when govt taxes, multiplier works in reverse
-Why? Because $ is now leaving the circular flow
-tax multiplier= -MPC/(1-MPC) or -MPC/MPS **note: it's negative
-if there is a TAX-CUT, then multiplier is (+) b/c there is now more $ in circular flow