A computer implemented method of making an investment value decision through modeling an investment's expected cash flows, each expected cash flow represented on the display device of a computer as a graphical three-dimensional joint-probability volume encapsulating uncertainties of both time and magnitude, making it unnecessary to consider investment risk before choosing discount rates, allowing a user to discount all cash flows using only the “risk-free” rate to produce a net present value probability distribution rather than single-number estimate, and displaying the resulting net present value probability distribution as a graphical two-dimensional net present value probability area on the display device of a computer, wherein one dimension represents magnitude and the other dimension represents probability.