A Few Data Points (**See 3//5/2019 Edit**)
- From 1986-2018, the US has increased its World Market Share from 30% to 54%
- The US outperformed Int'l by over 3.5% CAGR over these 33 years
- In 1989, the US fell to its lowest world share of 18% of World Cap in recent history

Reasons to Reconsider Overweighting US
- International Investing is more affordable than ever with VTIAX and VTWAX low ER's
- The current World Cap is within spitting distance of a Vanguard's recommended 60/40 equity allocation
- The US has it's highest relative valuation to the rest of the world that it has ever had in modern history
- Unless you are absolutely convinced the US is going to gain World cap share to the tune of 60% - 80%, you might reconsider.
- Home Country Bias is a real risk, even for the US, albeit a much lower one than others. Do not assume is it near zero due to a nice track record.
How many US investors in 1989 would have been comfortable with a 18% US / 82% Int'l portfolio? Probably not many considering the added expense, political, and currency risk. If those investors had overweighted the US heavily, they have been handsomely rewarded over the past 30 years and had their strategies well-justified in their minds all these years later. Looking at this time period as a justification for the next 33 years might be very risky.
Let's say you switch from 100% US to 100% Total World right now (Currently 54% US / 46% Int'l)
- If the US charges toward a 60-80% of World Cap, you will enjoy significant returns
- If the US finds itself back at 25-50% of World Cap at any point for any reason, you will have made the right call
---- If the US undergoes a significant recession and the rest of the world doesn't as much, you will be covered
---- If there are no major recessions worldwide, but Int'l wildly outperforms US, you will be covered
The more I evaluate the reasonable cost of international exposures, along with the current market weights and valuations, the more I am starting to believe that RIGHT NOW is the best time for a US investor to consider Total World compared to any point in the past 30-40 years. Would love to hear some feedback!
EDIT 3/5/2019: One user has challenged me on the accuracy of the graph above - especially the US capitalization in the 1980's - since other sources cite otherwise. To arrive at the data above, I used backtesting of Total US and Global-Ex US indexes with no re-balancing to arrive at the current weights. In my mind, this should have painted an accurate picture looking back, but maybe not. It may depend on which indexes have been piecewised together to cover this time period for each source. Vanguard has published a paper in Feb 2019 that shows higher US weights during the 1980's (Link below). Take what you will from my post, Vanguard's paper, and all other sources. I will say I have enjoyed all of your thoughts and feedback on the Total World approach through your contributions in this thread.
Global equity investing: The benefits of diversification and sizing your allocation
https://www.vanguard.com/pdf/ISGGEB.pdf
EDIT 4/29/2019
This graphic below appears to be more accurate and covers many more years than my original backtesting result. Unless an investor feels confident they could have predicted any portion of this graph, or can extrapolate it in a meaningful way going forward, Total World should at least be strongly considered as a reasonable starting point.
1900-2017 via Credit Suisse
