The country's public debts will expand to 529 trillion yen by March 1999, a figure bigger than the nation's economy, the Finance Ministry announced Wednesday.The outstanding long-term debts of local and the central governments combined are expected to exceed forecasts for the nation's gross domestic product as of the end of fiscal 1998 and total roughly 529 trillion yen, the ministry said.GDP as of the end of fiscal 1998, which begins in April, is expected to be roughly 520 trillion yen, according to the Economic Planning Agency. Ministry statistics show that the debts will be about 40 trillion yen greater than the 489 trillion yen currently projected for the end of March, the end of fiscal 1997.Officials said one main factor behind the increase was the roughly 16 trillion yen worth of long-term debts festering from the now-privatized Japanese National Railways. Another 10 trillion yen worth of new debts are government bonds convertible upon request that would be granted to the Deposit Insurance Corp. as part of the government's efforts to stabilize the financial system.