  In this paper, we use replica analysis to determine the investment strategy
that can maximize the net present value for portfolios containing multiple
development projects. Replica analysis was developed in statistical mechanical
informatics and econophysics to evaluate disordered systems, and here we use it
to formulate the maximization of the net present value as an optimization
problem under budget and investment concentration constraints. Furthermore, we
confirm that a common approach from operations research underestimates the true
maximal net present value as the maximal expected net present value by
comparing our results with the maximal expected net present value as derived in
operations research. Moreover, it is shown that the conventional method for
estimating the net present value does not consider variance in the cash flow.
