The CIA drone campaign began in Yemen in 2002 and in Pakistan in 2004.
Drone strikes in Pakistan rose steadily under President Barack Obama in 2009, to their peak of 122 in 2010.
Starting in 2011, strikes in Pakistan began to decline, while they spiked in Yemen, particularly as the Obama administration began using drones to support the Yemeni government's battles against al-Qaeda-linked militants in 2012.
The civilian and "unknown" casualty rate from drone strikes has fallen steadily over the life of the program.
PAKISTAN: The casualty rate in Pakistan for civilians and "unknowns" -- those who are not identified in news reports definitively as either militants or civilians -- was around 40% under President George W. Bush. It has come down to about 7% under President Obama.
PAKISTAN: Only 58 known militant leaders have been killed in drone strikes in Pakistan, representing just 2% of the total deaths.
PAKISTAN: In 2012, 2% of the drones' victims were characterized as civilians in news reports and 9% were described in a manner that made it ambiguous whether they were militants or civilians.
PAKISTAN: In 2013, civilian casualties are at their lowest ever. That is partly the result of a sharply reduced number of drone strikes in Pakistan -- 26 so far in 2013, compared with a record 122 in 2010 -- and also more precise targeting.
YEMEN: The civilian and "unknown" casualty rate over the life of the drone campaign is 14-15%.
YEMEN: U.S. drones have killed at least 35 key al-Qaeda militants, including the Yemeni-American cleric Anwar al-Awlaki on September 30, 2011, and Fahd al-Quso, who was suspected of involvement in the 2000 bombing of the USS Cole.
YEMEN: In 2013, civilian casualties are at their highest ever. This is largely due to a single drone strike that killed between 11 and 15 people are they headed to a wedding on December 12.