Civilian casualties from U.S. drone strikes in Pakistan have dropped precipitously, observes CNN national security analyst Peter Bergen in a new posting on CNN's Opinion page.

According to data collected by Bergen and his colleages at the New America Foundation, the estimated civilian death rate in U.S. drone strikes in Pakistan has declined dramatically since 2008, when it was at its peak of almost 50%. Today, for the first time, the estimated civilian death rate is at or close to zero.

The data is generated by averaging the high and low casualty estimates of militant and civilian deaths published in a wide range of media outlets.

The drop in the number of civilian casualties since 2008 came as a result of several developments, one of which was a directive issued from the White House just days after President Obama took office, to tighten up the way the CIA selected targets and carried out strikes. Bergen also writes that CIA's use of smaller, more accurate munitions and improved drone capabilities have helped.

Pakistani officials now rarely base their criticism of U.S. drone strikes on the incidence of civilian casualties and instead point, quite reasonably, to another objection: the U.S. violation of Pakistan's national sovereignty, Bergen notes. The Obama administration maintains that international law does not prohibit the use of lethal force against an active enemy "when the country involved consents or is unable or unwilling to take action against the threat."

Read Peter Bergen's whole article here