I've obtained the following file from the US Census Bureau.
I've been working with these files and have noticed some issues with the results so I decided to investigate the tools I was using to see if they have something to do with the problem.
Steps to reproduce the problem:
Download the census shapefile from ftp://ftp2.census.gov/geo/tiger/TIGER2012/UNSD/tl_2012_42_unsd.zip.
Open shapefile with qgis.
Select Plugins>mmqgis>Transfer>Geometry Export to CSV file.
Pick a location to save the file.
Using QGIS, select Plugins>mmqgis>Transfer>Geometry Import FROM CSV file.
It will take a moment to run and then it will display the imported data. The issue should be fairly evident as there are several large polygons that are missing.
Does anyone know what is causing this? Thanks.