The ratio of increase in income to increase in investment is termed as

Investment Multiplier.

The correct answer is Option (4) → Investment Multiplier.

The Investment Multiplier measures how much income increases as a result of an increase in investment.

It is defined as:

Multiplier (K)=ΔY / Δ I , where

• ΔY = Change in income

• ΔI = Change in investment