Pension schemes in Nigeria have run under several operational regimes. Some schemes are with legacies of failures suffering pensioners to the point that some times, retirees die without getting their pension pay outs. This work studies these schemes as reviews and focuses on the new contributory pension scheme of June 2004. Calibrated linear model is applied to check the optimality of current regulation-guided portfolio class compared to 2 other portfolio classes. This simulations uses asset under management as scarce resources constrained on limitations of investment ratios of 3 different asset classes. All results and values from PFAs (Pension Fund Administrator) are based on Nigeria's investment environment within the period under study. This work provides a mathematical model usable to evaluate returns of PFAs. It also advices for approval of other portfolio classes to allow best result from asset class spread for a better performance of contributors' fund in Niegria.