Cumulative net value = unit net value+dividend. If you don't pay dividends during the investment period, then your income is market value = unit net value * share-cost; If you have dividends (cash dividends), then your income = unit net value * share+cash dividends-cost; If dividends are reinvested, then your income = unit net value * share cost. If a fund is measured, its income is measured by its accumulated net value.