A German research institute predicts if the two Koreas were to unify following North Korea’s abrupt collapse, unification costs would be 24 percent of the South’s gross domestic product.

Halle Institute for Economic Research President Ulrich Blum made the projection in a contribution to German daily Bild on Tuesday.

Blum based the assessment on economic figures recorded by East and West Germany in 1990 at the time of their unification.

He said while the South should prepare for unification, efforts are bound to run into difficulties without cooperation from the North.

Blum said the South could consider advancing into the North with a strategy to build special economic zones. But he added it is evident from the Gaeseong Industrial Complex that it is hard for such projects to succeed without fundamental changes in the North’s institution.