# How to annualize dividends paid at varying intervals?

I am attempting to write a function that will calculate the annualized rate of return for individual dividends made by illiquid investments. These dividends are paid at varying intervals and the illiquid investment does not have an observable market price.

I have looked at using:

    [(1 + YTD ROR)1/(#of days/365)] – 1


However, this does not seem valid if this dividend is one of many that have been made this year.

Below are 3 sample cases:

A Investment
$10 / 1 unit 1/31/2011 -$0.11 div / 1 unit  - 1.1% ROI - 4.4% annualized ROI
4/30/2011 - $0.08 div / 1 unit - 0.8% ROI - 3.2% annualized ROI 7/31/2011 -$0.10 div / 1 unit  - 1.0% ROI - 4% annualized ROI


For investment A the assumption is being made that each dividend paid was being paid on a quarterly basis

B Investment
$10 / 1 unit 1/31/2011 -$0.11 div / 1 unit  - 1.1% ROI - 13.2% annualized ROI
2/27/2011 - $0.10 div / 1 unit - 1.0% ROI - 12% annualized ROI 3/30/2011 -$0.10 div / 1 unit  - 1.0% ROI - 12% annualized ROI


For investment B the assumption is being made that each dividend paid would be paid monthly.

C Investment
$10 / 1 unit 5/30/2011 -$2.00 / 1 unit - 20% ROI - 48.6% annualized ROI (assuming 365 days in a year)