Drive Time results when polygon cuts thru block aggregated data?

Question

How does Business Analyst report calculate, for example, 'total households' in a 20-min drive time polygon when the household data is aggregated at the block level and the 20-min drive time polygon cuts thru the actual block polygons on the outside edges?  I'm assuming Business Analyst returns a household count for those block records only partially included in the drive time polygon based on the geographic area of that block that is contained inside the drive time polygon.  If half of the block is inside the drive time polygon, then half of the total households are included in the drive time total for that block record.   Is this correct?

Jason_RobinsonRobinson · Answer

I can add a few details here.  Business Analyst Pro will default to hybrid out of the box however if Business Analyst Desktop is also installed it will follow the apportionment selections in Business Analyst Desktop>Preferences>Data tab.

I believe one can create a statistical data collection (BA Pro's version of a customer BDS layer) to create a layer used for enrichment with a different apportionment setting but admittedly this is something that should be possible though I have not personally tried yet.

Regards,
Jason R.

Fasil · Answer

Hello Jack,

The following documentation will explain how data apportionment works in Business Analyst.

1. Calculation estimates for user-created areas—Business Analyst Web App | Documentation

2. About Data Enrichment—Esri Demographics | Documentation

I hope this helps!

Fasil T.

Business Analyst Team

SusanZwillinger · Answer

In Business Analyst desktop, you can set you preferences for how the data is aggregated.  The most accurate method is to use the "Block Appointment" method.  This uses 6+ million Census block points to apportion the number of households within the Census block group that is intersecting your drive time area.  This allows you to model a situation where the distribution of households is not homogeneous throughout the block group area that is within the drive time area.  Thus, if the area of the block group is split 50/50 inside/outside the drive time area but there is a 90/10 split for the number of households, you'll get the 90% of households for that block group and that percentage can be used to apportion other household based data.

In ArcGIS Pro Business Analyst and Business Analyst Web App, I think the "Enrich Layer" option and the BA reports use block apportionment, but I have not checked that.  For performance, it might also use the hybrid approach.