Why Has North Korea Responded Positively to the Nuclear Talks in 2007?

There are three key economic sanctions placed against North Korea that are still in effect: denial of MFN status, placement on a list of countries supporting international terrorism, and financial tightening following the Proliferation Security Initiative. North Korea's annual trade deficit is approximately one billion dollars. The latest series of economic sanctions made it very difficult for North Korea to continue to finance a trade deficit through illicit means. North Korea responded positively to the nuclear talks in 2007 partly because of the series of financial sanctions levied against it since 2003, and partly because of the changed approach of the North Korean leaders toward a greater calculation of benefits and costs since the collapse of the Soviet Union. This means that increasing benefits to North Korea in relation to costs should make the peace proposal more appealing to the North Korean leaders, and this is exactly what the U.S. negotiators seem to have been doing in the latest nuclear talks.