Changes

===Patent start-end table===

To construct the table of all patents and their grant dates and expiration dates (i.e., start-end of being an active patent), we did the following:

(code/detailed documentation is in <code> E:\mcnair\projects\LBO\Clean\Building the Patent Start End Table.txt</code>)

*Imported lookup table '''patentExpirationRules.txt''' containing patent lifetime implied by each maintenance event

*For each patent, found the latest expiration date implied by any recorded maintenance event.

==STATA analysis==