De Reyck, Bert; Grushka-Cockayne, Yael; Lockett, Martin; Calderini, Sergio Ricardo; Moura, Marcio; Sloper, Andrew: The impact of project portfolio management on information technology projects; in: International Journal of Project Management, Vol. 23 (2005), No. 7, pp. 524-537.
In their article de Reyck et al. argue that project portfolio management (PPM) is essential to create value with IT project. The research focus is the management of resources and risk. Moreover most articles are from vendors of the software, promoting the value of the PPM process, a claim not based on any empirical evidence.
Based on findings from a survey about PPM adoption, de Reyck et al. introduce a three-stage classification scheme of PPM adoption. Furthermore they show that a strong correlation exist between increasing adoption of PPM processes and a reduction in project related problems, and between PPM adoption and project performance.
Their maturity model shows how the elements of PPM (centralisation of project control, financial analysis, risk analysis, interdependencies, constraints, overall portfolio analysis, categorisation/selection/accountability and governance, optimisation, and specialised software) are adopted in each of their 3 stages:
from: De Reyck et al. (2005), p. 530
In my opinion the question remains if organisations in stage 3 follow a controlling agenda more than they actually empower their project managers.