(CNN) -- President Obama is celebrated and criticized for greatly accelerating the number of CIA drone attacks in Pakistan, but the similar covert war that he has launched in Yemen has received considerably less attention. The Obama administration has launched an estimated 28 drone strikes and 13 air strikes in Yemen, according to data compiled by the New America Foundation from reliable news reports. By contrast, the administration of George W. Bush only launched one drone attack in Yemen. (The data was gathered from media outlets that include the Associated Press, Reuters, CNN and the Yemen Post.) On April 25, the White House approved a new policy inaugurating a more aggressive campaign of drone strikes in Yemen allowing so-called "signature" strikes. These are strikes on individuals whose patterns of behavior signal the presumed presence of an important militant or of a plot against the United States, even if the targeted individual's identity is unknown.
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U.S. drone attacks in Yemen haven't received as much attention as in Pakistan
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Dozens of airstrikes have killed hundreds, mostly AQAP terrorists, the authors say
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In April, White House approved policy for even more aggressive campaign of drone strikes
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A Yemen expert says the strikes haven't dented AQAP's overall strength
Counting drone attacks and airstrikes in @placeholder is complicated because it has often been unclear whether attacks were launched from drones or from fighter jets, and villagers regularly provide conflicting accounts of the kinds of aircraft used in these attacks.