How is the 2-year impact calculated for institutions?
The institution's 2-year impact for year X equals the citations received in year X to items affiliated with Los Alamos National Laboratory and published in years X-1 and X-2, divided by the number of citable items from those two years. This follows the same formula as journal impact factors but is computed independently from citation and affiliation data — it has no connection to journal impact factors and does not reflect the impact factors of the journals in which Los Alamos National Laboratory's work appeared.
