As I recall there is no science in selecting asset classes and percents - hopefully armed with data on rolling correlations and knowledge/data of the 'long term' expected growth of the asset classes you've selected - it's a crap shoot.
And and those correlations vary over time(hence the rolling word) and and hopefully you enter selected asset classes a good aka value buy point points cause some have irritatingly long trends(??gold, long bonds, etc) before they revert trends.
Which is why I'm a Boglehead - in retirement - I just buy Vanguard's best shot - aka Target Retirement and try to buy middle of the road dividend stocks with my side money.
heh heh heh heh heh - a little razz to stir up the slice and dice crowd. Ie what's global -
cap weight, regional selection and ignore mrkt cap or trying to select what's cheap at time you have money. What happens when the rolling correlations change - hold the line or change asset classes??