That is an interesting model they came up with. In their defense, they do admit it’s shortcomings – particularly:
“The most significant potential drawback to this or any model-based approach is that time series modeling assumes a predictable continuation of historical patterns and relationships and therefore is likely to have some difficulty producing reliable estimates at economic turning points or during periods when there are sudden changes in trend. BLS will continue researching alternative model-based techniques for the net birth/death component; it is likely to remain as the most problematic part of the estimation process.”
It is definitely missing on this account – not only does it have the addition of 49 construction firms in April, but it also calculated the addition of 26 financial activities – that latter number certainly includes a number of things other than mortgage companies – but I think it is safe to say that it is “slightly” overestimating the number of new fincancial companies.