If I understand it correctly, you're saying that The Economist based an article on your research, and you're spurned, because they didn't give you a byline or e

If I understand it correctly, you're saying that The Economist based an article on your research, and you're spurned, because they didn't give you a byline or even a hat-tip. That's not plagiarism. Plagiarism would be if they copied and perhaps edited paragraphs of your writing; they didn't do that, they used the data, and seriously reworked the presentation. If you had an agreement, perhaps in e-mail, that you'd receive credit, that's breach of contract. Their articles are usually well researched, and it is likely that you were not the only source. I'm sorry that you feel like you've been tricked, but you shouldn't do hours and hours of volunteer work for a newspaper (or any company) without first establishing what you'll be getting out of it, preferably in writing. The journalist therefore probably didn't realize you felt strongly about it, and when you asked them subsequently, maybe took an offence?