Mr. Taylor:

Q1 - How often does this data get updated?
A1 - I download the file every month, around the 10th.  

Q2 - is this data from the year 2000 or what is the term?
A2 - The data comes from the Emission Inventory Questionnaire (EIQ), submitted by each company that meets or exceeds the emissions tracking threshold established by the EPA & TNRCC.  The EIQ's are an annual report.  TNRCC is usually about 1 year behind the current year in the QA process for data submitted.  At the present time the year 2000 data is being downloaded to the TNRCC Point Source Database (PSDB) which is the database used to obtain the State Summary File.  Please excuse my long winded answer.  

FYI, you might be interested in a data file called the Major Emissions file.  It is a listing of all companies in TX that meet or exceed specific emissions threshold tracking criteria.  This file is a subset of the State Summary file.  If you want to know more, let me know.  
Jim Parks
PH     512 239-2544
FAX   512 239-0888
jparks@tnrcc.state.tx.us