One of the controversies in growth analysis is the relative role of capital accumulation and productivity growth in driving output growth. As we interpret the evidence, discussed in this paper, part of the controversy on the role of capital accumulation in the growth process is due to the time span of the analysis (growth transitions versus steady states/long run growth). In fact, the empirical importance of various growth determinants will depend on what we want explain: long run growth, say growth over half a century or a century as different from growth dynamics over one or two decades. New evidence is showing that growth fluctuations at frequencies of a decade or so are very important part of the growth story for many developing countries. Growth is an irregular and volatile process in which the same country may experience shifts in growth regimes that can entail growth take-off and booms, stagnation and/or growth collapses. In this context, investment and savings become important variables whose determinants and dynamics we want to understand for designing public policies affecting positively the rate of economic growth.