China Locks Info on the Nation Inside a Black Field

China’s party-state, long steeped in secrecy, is creating a black box around information on the world’s second-largest economy, alarming global businesses and investors.

Prodded by President Xi Jinping’s emphasis on national security, authorities in recent months have restricted or outright cut off overseas access to various databases involving corporate-registration information, patents, procurement documents, academic journals and official statistical yearbooks.