"USA" ha sido el mercado mas rentable de los últimos 100 años, el SP500 o el Nasdaq han ganado a España, al Mundo, etc. y supongo que seguiran asi.
U.S. investors could look at past performance, even long-term performance, and conclude that there is no point investing in European equities. One dollar invested in MSCI Europe (USD) in 1970 is now worth $56. One dollar in the S&P 500 over the same period would have grown to $106 today.
Yet on closer examination, this is a perfect example of statistics reporting the facts but hiding the truth. Thanks to the power of compounding, performance over the last few years has had a huge effect on long-term returns.
From 1970 to 2009, the S&P 500 compounded at 9.87%, and MSCI Europe at 9.88%. The entire outperformance of the last 47 years occurred during the last seven years.
That underperformance, combined with investors’ attitudes toward European stocks — which are apathetic at best — has caused the valuation gap between U.S. and European equities to widen into a gulf. The cyclically adjusted price-to-earnings ratio, or CAPE, measures the price to real earnings over the last ten years. The ratio for the United States is 30 and for European equities it’s just 17.
http://thereformedbroker.com/2017/05/24/what-were-telling-clients-about-european-stocks/
La bolsa ha estado estancada casi 20 años, en el "Crack del 29" y en la "Crisis de los 70", hay que estar cubierto por si acaso.
Nada garantiza que ese crack no se dará al año 20 de empezar a invertir, invertir de golpe te va a dar con una seguridad de casi el 100% más rentabilidad que hacer DCA durante 20 años. Ningún estudio que yo haya visto puede justificar un DCA de 20 años.