However, not all of the difference between the g -factors for electrons and muons is exactly explained by the Standard Model. The muon g -factor can, in theory, be affected by physics beyond the Standard Model, so it has been measured very precisely, in particular at the Brookhaven National Laboratory. In the E821 collaboration final report in November 2006, the experimental measured value is 2.002 331 8416 (13), compared to the theoretical prediction of 2.002 331 836 20 (86). This is a difference of 3.4 standard deviations, suggesting that beyond-the-Standard-Model physics may be a contributory factor. The Brookhaven muon storage ring was transported to Fermilab where the Muon g –2 experiment used it to make more precise measurements of muon g -factor. On April 7, 2021, the Fermilab Muon g −2 collaboration presented and published a new measurement of the muon magnetic anomaly. When the Brookhaven and Fermilab measurements are combined, the new world average differs from the theory prediction by 4.2 standard deviations.