1. A computer program product, comprising a computer readable storage medium having a computer readable program code stored therein, said computer readable program code containing instructions configured to be executed by a processor of a computer system to implement a method for reducing a cost of ownership of a portfolio of N software applications, said method comprising the steps of: identifying a regression function for each software application of the N software applications, wherein each regression function expresses an approximate cost of ownership of the application in terms of at least one parameter and at least one undetermined coefficient, wherein N is at least 2; selecting J applications A 1 , A 2 ,. .. , A j from the N applications such that a remaining N-J applications of the N applications are unselected, wherein J<N, wherein the coefficients in the regression functions for the N-J unselected applications constitute a subset of the coefficients in the regression functions for the J selected applications, and wherein F j represents the approximate cost of ownership of the application A j for j=1, 2,. .. , J; determining the coefficients in the regression functions for the J selected applications so as to minimize a function H=Σ j W j |F j −G j | P , wherein G j is an actual cost of ownership of application A j for j=1, 2,. .. , J, wherein Σ j represents a summation over j from j=1 to j=J, wherein P>0, and wherein W j are predetermined weights subject to W j >0, wherein said determining the coefficients comprises computing said coefficients, said computing comprising utilizing a numerical value of each parameter in each regression function relating to the J applications; calculating a regression total cost of ownership C REGR of the N applications, said calculating comprising summing the N regression functions associated with the N applications including utilizing the computed coefficients and a numerical value of each parameter relating to the N applications; ascertaining whether C REGR differs from C EST by more than a tolerance selected from the group consisting of a pre-determined cost differential and a predetermined percent, wherein C EST is an estimate of a total cost of ownership of the N applications; if C REGR differs from C EST by more than the tolerance then iterating until C REGR does not differ from C EST by more than the tolerance, wherein each iteration of the iterating comprises selectively re-executing the identifying, selecting, determining, calculating, ascertaining, and iterating steps; choosing at least one control parameter from the parameters in the N regression functions such that the remaining parameters in the N regression functions are unselected; specifying permissible values for each control parameter of the at least one control parameter, wherein the permissible values for each control parameter are independently selected from the group consisting of a discrete set of values, at least one continuous range of values, and a combination thereof; expressing a total cost of ownership (T) of the N applications as a sum of the N regression functions associated with the N applications such that T is a function of the at least one control parameter, wherein the computed coefficients and a numerical value for each unselected parameter appears in T; and determining a value for each control parameter of the at least one control parameter so as to minimize T subject to the permissible values; transmitting the value for each control parameter to an output device of the computer system; maintaining each application of the N applications and utilizing and maintaining all instances of each application of the N applications at the minimized T with each control parameter of the at least one control parameter being at its determined value at which T is minimized.