Measuring the impact of new technologies on productivity has been a classic question in economics. However very little works have been focused on the revolution of the modern office place for knowledge workers. In this paper, we study the diffusion of Microsoft SharePoint, a new technology aimed to bring seamless collaboration for Microsoft Office documents, serving as a direct substitute for traditional email attachments.  We propose a new type of staggered difference-in-difference estimator to measure the effect of SharePoint adoption. Through a parametric model of the adoption diffusion process, the proposed estimator allows us to account for latent variables that may modulate inter-temporal shocks before adoption. We show that our estimator works well in simulations and our empirical results show that the traditional email attachments can be reduced by 25 pieces per user after 10 months of adoption of SharePoint.