Abstract: Everything in our universe is made of matter and not antimatter, and we do not understand why. An exciting possibility is that this asymmetry between baryons and antibaryons was created during the electroweak phase transition, when all elementary particles became massive, in a process called electroweak baryogenesis. The scenario requires new physics at the electroweak scale, which can be tested by current and upcoming experiments.  Unfortunately, theoretical predictions for the baryon asymmetry may vary by orders of magnitude, depending on the calculational method used. A careful and systematic analysis of the so-called vev-insertion-approximation scheme shows that this approach is much less efficient than previously thought.