Facebook has moved to improve its advertising measurement errors by expanding its partnership with the global marketing firm Nielsen. Previously, the two companies worked together to create a marketing tool that measured campaign reach in 17 countries. This has now been expanded to cover 25 countries. Facebook has also expanded its relationship with ComScore in the US in order to verify the social media network's video impressions, and measure the performance for “Facebook properties”. The announcement from Facebook said that its partners will now “provide metrics on when a display ad enters the Facebook screen and when the entire ad appears on the screen”.