Thomas Palley has a write-up on the stagnation debate on his blog:
Explaining Stagnation: Why it Matters
Larry Summers (here) and Paul Krugman (here) have recently identified the phenomenon of stagnation. Given that they are giants in today’s economic policy conversation, their views have naturally received enormous attention. That attention is very welcome because the issue is so important. However, there is also a danger that their dominance risks crowding out other explanations of stagnation, thereby short-circuiting debate.
Krugman has long emphasized the liquidity trap – zero lower bound to interest rates which supposedly prevents spending from reaching a level sufficient for full employment. Summers has added to this story by saying we have been in the throes of stagnation for a long while, but that has been obscured by years of serial asset price bubbles.
That is a good start to the conversation, but there are other views that dig deeper regarding the causes of stagnation.
Read more here