Software development effort estimation is a very important issue in software engineering and several models have been defined to this end. In this paper, we carry out an empirical study on the estimation of software development effort broken down by phase, so that estimation can be used along the software development lifecycle. More specifically, our goal is twofold. At any given point in the software development lifecycle, we estimate the effort needed for the next phase. Also, we estimate the effort for the remaining part of the software development process. Our empirical study is based on historical data from the ISBSG database. The results show a set of statistically significant correlations between: (1) the effort spent in one phase and the effort spent in the following one, (2) the effort spent in a phase and the remaining effort, (3) the cumulative effort up to the current phase and the remaining effort. However, the results also show that these estimation models come with different degrees of goodness of fit. Finally, including further information, such as the functional size, does not significantly improve estimation quality.