To calculate the percentage change in the factor-weighted index, you use the formula:
Percentage Change=(New Index Value – Old Index ValueOld Index Value)×100Percentage Change=(Old Index ValueNew Index Value – Old Index Value)×100
The factor-weighted index is the sum of the products of stock prices and their respective ratios of annual revenues.
Initial Index Value: 1×200+2×400+3×800=200+800+2400=34001×200+2×400+3×800=200+800+2400=3400
Final Index Value: 1×400+2×600+3×900=400+1200+2700=43001×400+2×600+3×900=400+1200+2700=4300
Percentage Change: (4300−34003400)×100=9003400×100≈26.47%(34004300−3400)×100=3400900×100≈26.47%