The last study I saw might have been from 18 months ago, but they found that AI costs programmers more time than they saved AND that programmers completely miscalculated the efficiency of AI, unaware that it was slower.
Whether or not AI is more efficient now, it's demonstrated that individual programmers are pretty bad at evaluating AI efficiency subjectively.
That leaves the reports of CEO's, desperate to justify layoffs from lack of work with AI, desperate to goose their stock prices by being AI-first, and the slavish business press who exclusively repeats whatever they say.
Citation definitely needed.