Brendan O'Reilly, a guest expert at Geopolitical Intelligence Services, wrote, "A dark scenario of demographic decline sparking a negative feedback loop of economic crisis, political instability, emigration and further decreased fertility is very real for China".[51][52] Nicholas Eberstadt, an economist and demographic expert at the American Enterprise Institute, said that current demographic trends will overwhelm China's economy and geopolitics, making its rise much more uncertain. He said, "The age of heroic economic growth is over."[53]