All these economic/demographic studies suffer from a fundamental flaw. They assume that trends will continue to hold for a long time. Nothing could be further f

All these economic/demographic studies suffer from a fundamental flaw. They assume that trends will continue to hold for a long time. Nothing could be further from the truth, because any trend tends to correct itself, unless some disaster happens. For example, the trend of economic growth for several countries, including USA and China, is widely speculative because doesn't consider the changes in policy that can take place as soon as the next few months. Similarly for demographic concerns: a single change in policy or an external event can change the trends dramatically.