of virtually all cross-sectional analyses. If this homogeneous assumption is false, then cross-sectional observations are being drawn from different populations. While one can use estimation techniques such as fixed-effects to control for different population means, co-variances can also differ across populations (meaning behavior differs across populations) and the only way one can control for this aspect is to run regressions on each population separately. This means that the "laws of the marketplace" differ across populations, directly contradicting one of the main presumptions of using the PIMS data base for analysis. Telis and Golder (1996) claim that PIMS defines markets too narrowly. Respondents described their market very narrowly to give the appearance of high market share. They believe that this self reporting bias makes the conclusions suspect. They are also concerned that no defunct companies were included, leading to "survivor bias". See also Strategic management Marketing strategies Business model Benchmarking References Buzzell, R. and Gale, B. (1987) The PIMS Principles: Linking Strategy to Performance, Free Press, New York, 1987. Mintzberg, H. Ahlstrand, B. and Lampel, J. (1998) Strategy Safari: A guided tour through the wilds of strategic management, The Free Press, New York, 1998. Schoeffler, S. Buzzell, R. and Heany, D. (1974) Impact of Strategic Planning on Profit Performance, Harvard Business Review, March–April, 1974. Tellis, G. and Golder, P. (1996) First to Market, First to Fail: The Real causes of enduring market leadership, Sloan Management Review, vol. 37, no. 2, 1996. Ceccarelli, P. and Roberts, K. (2002) I nuovi principi PIMS: la gestione dell'impatto sul profitto, Sperling & Kupfer, Milano, 2002. Pedram Farschtschian: Private Equity für die Herausforderungen der neuen Zeit: Strategists Innovation für das Funktionieren von Private Equity im 21. Jahrhundert. Campus Verlag, Frankfurt 2010, Business intelligence terms Marketing strategy Databases