$1.3 trillion surge in the market capitalisation of gold and silver amid rising US government debt, TKL Against the backdrop of an unprecedented increase in US government debt, yields on long-term US Treasury bonds have reached their highest level since 2008, according to analytics firm The Kobeissi Letter (TKL). The Fed is no longer able to contain rising bond yields, while the White House cannot afford higher yields because of the enormous cost of servicing the national debt.