For high quality software, software requirements must be complete. In practice, not all software requirements are complete. In case of incomplete software requirements, software engineers fill in the requirements' gaps by getting feedback from the stakeholders or by making explicit or implicit assumptions. Explicit assumptions can be validated during analysis, while implicit assumptions validation is carried to design and implementation. Thus, compared to implicit assumption, explicit assumptions are better. Software requirements specifications change during different phases of project life-cycle. In an attempt to improve software development processes, we conducted an empirical study to search possible relationships between the number of implicit assumptions made by software engineers and requirements' volatility. This practice paper presents data from three completed projects at one CMMI level 3 company. Within the limit of our data set, our experience shows that possible relationships between projects' requirements volatility and the number of implicit assumptions are worth studying.