Oregon Center for Public Policy:

"Over the decades, corporate income tax contributions in Oregon have declined dramatically.... The decline of Oregon corporate income taxes is the result of corporations gaming the system. The principal ways they have done so are by obtaining numerous tax subsidies and loopholes at both the state and federal level, by pursuing aggressive tax sheltering strategies, and by taking advantage of new corporate forms largely exempt from corporate income taxes."

http://www.ocpp.org/2016/06/29/executive-summary-corporate-tax-decline/

A while back someone wrote that the Oregon state legislature had been passing out tax credits "like candy". It adds up to a substantial amount of tax money that is never collected.

I've also read that where businesses decide to locate doesn't have a lot to do with taxes. Probably more about markets and employee availability, which depends on the educational system.