  Recent research on the decline in the paper disruption index (D-index) has
sparked heated debates among scholars and garnered significant attention from
policymakers and research institution leaders globally. To bridge the gap
between policymakers' interest and scholars' skepticism about the D-index, we
present this article summarizing key insights from our eight-year
investigation, including interviews with scientists across nine disciplines and
an analysis of 41 million papers over six decades. Our work confirms the
decline in disruptive papers, addresses relevant technical concerns, and makes
several original contributions: we clarify that the D-index measures how new
ideas render old ones obsolete, suggesting 'Displacing' as an alternative
interpretation for 'D'; we show that federal funding agencies like the NIH and
NSF are less likely to support disruptive research; and we introduce the
'principle of functional equivalence' to explain the origins of recombining and
displacing mechanisms in science, stressing that not all innovation problems
are combinatorial, and challenging the belief that AI is the mature solution to
scientific innovation. This article aims to promote broader and more accurate
use of the D-index in research evaluation and to inspire new funding mechanisms
for scientific breakthroughs.
