&gt;<i>... $420B in new non-offset spending. ... It&#x27;s about 2.3% of GDP.</i><p>This assumes GDP doesn&#x27;t plunge because of disincentives to work and&#x2F;or skyrocketing hiring costs for low-wage (now medium-to-high wage) workers.  We don&#x27;t have solid evidence of that not happening since no country has instituted basic income on the scale of 300 million citizens.<p>Your math model shares a common theme I see with many of these back-of-the-envelope calculations:  they all assume a static economy where <i>all the other variables</i> that are affected by UBI -- which in turn <i>also feed back into paying for UBI</i> -- are unchanged.  I&#x27;ve commented on this aspect elsewhere: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10172421" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10172421</a>