The TSPinvestor Plus is partially based upon economic data that has a release date as late as the 8th of the month.
The development of the Plus model/formula was done using the TSP fund data from the end of the month, not the 9th. I needed to verify that using the returns/gains from the 9th of the month would be nominally the same.
And so I set forth to verify. I computed the TSP monthly gains for each fund on the last business day prior to the 9th (which would allow for reallocation on the 9th). I ran these through the existing model/formula, and was surprised that it actually made the annual return rate improve by 0.5%.
So I am comfortable with allocating the Plus on the 9th of the month.
I might at some point recompute the model/formula based upon the new data – and it may improve the returns. But for now I’m leaving it as is.