Huge and growing debt – and not enough young working people to pay it down – is threatening to crush the global economy, a Goldman Sachs executive is warning.Andrew Wilson, the European chief executive of Goldman Sachs Asset Management, is urging "new ways of thinking" to generate growth to work off the debt – especially in light of an aging population, the Telegraph reports. "The demographics in most major economies – including the [United States], in Europe and Japan — are a major issue — and present us with the question of how we are going to pay down the huge debt burden," he says, the Telegraph reports."With life expectancy increasing rapidly, we no longer have the young, working populations required to sustain a debt-driven economic model in the same way as we've managed to do in the past."A case in point, he says, is Japan, where gross government debt has gone above 200 percent of gross domestic product, and where an aging population is adding pressure, the Telegraph reports."[This] is evidently not sustainable over the long term," he said.The Organization of Economic Cooperation and Development's secretary-general, Angel Gurria, said a cash stimulus and stronger growth alone won't be enough, the Telegraph reports."Japan's future prospects depend on ensuring fiscal sustainability over the long term. With a budget deficit of around 8 percent of GDP, the debt ratio is set to rise further into uncharted territory," he said.It's not all doom and gloom, Wilson says."The demographic shift means that we need to look to more creative policy, including immigration and workforce expansion in order to find ways to pay down debt," he says, the Telegraph reports."This is happening in Japan in the form of [prime minister] Shinzō Abe's drive to increase female labor participation and via efforts to boost inflation."The bank executive also said bouts of volatility when the U.S. Federal Reserve starts to raise interest rates should be expected – and that may not be a bad thing."In fact, I would view this as getting back to a more normal world," he says, the Telegraph reports."Moving out of an environment where there is a huge amount of government and central bank policy designed to provide certainty and liquidity and to dampen volatility is a healthy sign, not an unhealthy one."