Following the first release of data from the WMAP spacecraft in 2003, the determination by Becker that the end of reionization occurred at z ≈ 6 appeared to conflict with estimates made from the WMAP measurement of the electron column density. However, the WMAP III data released in 2006 now seems to be in much better agreement with the limits on reionization placed by observation of the Gunn–Peterson trough.