Paul M. Romer receiving his Prize from H.M. King Carl XVI Gustaf of Sweden at the Stockholm Concert Hall, 10 December 2018.

© Nobel Media. Photo: Alexander Mahmoud

Paul M. Romer after receiving his Prize at the Stockholm Concert Hall, 10 December 2018.

© Nobel Media. Photo: Alexander Mahmoud

Waiting for the award ceremony to start - Paul M. Romer, William D. Nordhaus, Frances H. Arnold and Donna Strickland just before they receive their medals and diplomas.

© Nobel Media. Photo: Alexander Mahmoud

Paul M. Romer and mrs Anna Wersäll at the Nobel Prize banquet in the Stockholm City Hall, 10 December 2018.

© Nobel Prize Outreach. Photo: A. Mahmoud

Paul M. Romer and his wife Professor Caroline Weber take to the dance floor in the Golden Hall after the Nobel Prize banquet dinner on 10 December 2018.

© Nobel Prize Outreach. Photo: A. Mahmoud

Paul M. Romer takes a closer look at his medal during a visit to the Nobel Foundation on 11 December 2018.

© Nobel Prize Outreach. Photo: A. Mahmoud

2018 laureates assembled at the Nobel Foundation on 12 December 2018. From left: physics laureate Arthur Ashkin's son Michael Ashkin, laureate in economic sciences William D. Nordhaus, physics laureates Donna Strickland and Gérard Mourou, chemistry laureates Sir Gregory P. Winter and George P. Smith, medicine laureates Tasuku Honjo and James P. Allison, chemistry laureate Frances H. Arnold, laureate in economic sciences Paul M. Romer and peace laureate Denis Mukwege.

© Nobel Prize Outreach. Photo: A. Mahmoud

Paul M. Romer arriving to the laureates' get together at the Nobel Prize Museum in Stockholm on 6 December 2018.

© Nobel Prize Outreach. Photo: A. Mahmoud

Paul M. Romer after signing a chair at the Nobel Museum in Stockholm. As part of their visit to the Nobel Museum all laureates are asked to sign a chair.

© Nobel Media. Photo: Alexander Mahmoud

Paul M. Romer during a press conference in Stockholm, 7 December 2018.

© Nobel Prize Outreach. Photo: A. Mahmoud