A street vendor walks in front of a billboard congratulating Ethiopia's Prime Minister Abiy Ahmed for his Peace Nobel Prize, in Addis Ababa on December 10, 2019. - Ethiopian Prime Minister Abiy Ahmed hailed the role played by ex-foe Eritrea in the Nobel Peace Prize he collected on December 10 for his efforts to resolve the long-running conflict between the two neighbours. (Photo by EDUARDO SOTERAS / AFP)

People walk in front of a billboard congratulating Ethiopia's Prime Minister Abiy Ahmed for his Peace Nobel Prize, in Addis Ababa on December 10, 2019. - Ethiopian Prime Minister Abiy Ahmed hailed the role played by ex-foe Eritrea in the Nobel Peace Prize he collected on December 10 for his efforts to resolve the long-running conflict between the two neighbours. (Photo by EDUARDO SOTERAS / AFP)

People walk in front of a billboard congratulating Ethiopia's Prime Minister Abiy Ahmed for his Peace Nobel Prize, in Addis Ababa on December 10, 2019. - Ethiopian Prime Minister Abiy Ahmed hailed the role played by ex-foe Eritrea in the Nobel Peace Prize he collected on December 10 for his efforts to resolve the long-running conflict between the two neighbours. (Photo by EDUARDO SOTERAS / AFP)

A picture taken in Addis Ababa on December 10, 2019 shows a billboard congratulating Ethiopia's Prime Minister Abiy Ahmed for his Peace Nobel Prize. - Ethiopian Prime Minister Abiy Ahmed hailed the role played by ex-foe Eritrea in the Nobel Peace Prize he collected on December 10 for his efforts to resolve the long-running conflict between the two neighbours. (Photo by EDUARDO SOTERAS / AFP)

US professor of medicine and co-laureate of the 2019 Nobel Prize in Physiology or Medicine William G. Kaelin receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonas EKSTROMER / POOL / AFP)

US professor of medicine and co-laureate of the 2019 Nobel Prize in Physiology or Medicine William G. Kaelin receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Henrik MONTGOMERY / POOL / AFP)

British physician-scientist and co-laureate of the 2019 Nobel Prize in Physiology or Medicine Sir Peter J. Ratcliffe receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Henrik MONTGOMERY / POOL / AFP)

US professor of pediatrics, radiation oncology, biological chemistry, medicine, and oncolog and co-laureate of the 2019 Nobel Prize in Physiology or Medicine Gregg L. Semenza receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonas EKSTROMER / POOL / AFP)

Polish author and co-laureate of the 2019 Nobel Prize in Literature Olga Tokarczuk sits next to Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke poses with his Nobel Prize during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke poses with his Nobel Prize during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Polish author and co-laureate of the 2019 Nobel Prize in Literature Olga Tokarczuk (C) applauds Austrian author and co-laureate of the 2019 Nobel Prize in Literature Peter Handke (3rdL) next to US professor of pediatrics, radiation oncology, biological chemistry, medicine, and oncolog and co-laureate of the 2019 Nobel Prize in Physiology or Medicine Gregg L. Semenza (L) during the Award ceremony 2018 on December 10, 2018 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Protesters in support of Myanmar's State Counsellor Aung San Suu Kyi stand in front of the Peace Palace of The Hague on December 10, 2019, following Aung San Suu Kyi's first day of hearing on the Rohingya genocide case. - Nobel peace laureate Aung San Suu Kyi faced calls for Myanmar to "stop the genocide" of Rohingya Muslims as she personally led her country's defence at the UN's top court on Tuesday. Myanmar's civilian leader sat through graphic accounts of mass murder and rape as the west African state of The Gambia set out its case at the International Court of Justice in The Hague. (Photo by Sem VAN DER WAL / ANP / AFP) / Netherlands OUT

A convoi of vehicles allegedly transporting Myanmar's State Counsellor Aung San Suu Kyi passes a group of protesters in support of the Rohingya in front of the Peace Palace of The Hague on December 10, 2019, following Aung San Suu Kyi's first day of hearing on the Rohingya genocide case. - Nobel peace laureate Aung San Suu Kyi faced calls for Myanmar to "stop the genocide" of Rohingya Muslims as she personally led her country's defence at the UN's top court on Tuesday. Myanmar's civilian leader sat through graphic accounts of mass murder and rape as the west African state of The Gambia set out its case at the International Court of Justice in The Hague. (Photo by Sem VAN DER WAL / ANP / AFP) / Netherlands OUT

Protesters in support of Myanmar's State Counsellor Aung San Suu Kyi stand in front of the Peace Palace of The Hague on December 10, 2019, following Aung San Suu Kyi's first day of hearing on the Rohingya genocide case. - Nobel peace laureate Aung San Suu Kyi faced calls for Myanmar to "stop the genocide" of Rohingya Muslims as she personally led her country's defence at the UN's top court on Tuesday. Myanmar's civilian leader sat through graphic accounts of mass murder and rape as the west African state of The Gambia set out its case at the International Court of Justice in The Hague. (Photo by Sem VAN DER WAL / ANP / AFP) / Netherlands OUT

US professor of pediatrics, radiation oncology, biological chemistry, medicine, and oncolog and co-laureate of the 2019 Nobel Prize in Physiology or Medicine Gregg L Semenza receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2019 on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Henrik MONTGOMERY / POOL / AFP)

Polish author Olga Tokarczuk (L) receives the 2018 Nobel prize from King Carl Gustaf (R) of Sweden during the Award ceremony 2019 on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonas EKSTROMER / POOL / AFP) / Sweden OUT

Austrian author laureate of the 2019 Nobel Prize in Literature Peter Handke receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony 2018 on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonas EKSTROMER / POOL / AFP)

Polish author and laureate of the 2018 Nobel Prize in Literature Olga Tokarczuk sits next to Austrian author and laureate of the 2019 Nobel Prize in Literature Peter Handke (R) during the award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Henrik MONTGOMERY / POOL / AFP)

US economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Abhijit Banerjee receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Abhijit Banerjee receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Abhijit Banerjee receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Abhijit Banerjee poses with his Nobel Prize during the award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

French-American economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Esther Duflo receives her Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

French-American economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Esther Duflo receives her Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

French-American economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Esther Duflo poses with her Nobel Prize during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

French-American economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Esther Duflo poses with her Nobel Prize during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer receives his Nobel Prize from King Carl XVI Gustaf of Sweden (R) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer (R) stands next to colaureates French-American economist Esther Duflo (C) and US economist Abhijit Banerjee (L) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer poses with his Nobel Prize during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer (R) is applauded by colaureates French-American economist Esther Duflo (C) and US economist Abhijit Banerjee (L) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

US development economist and co-laureate of the 2019 Nobel Prize in Economic Sciences Michael Kremer (R) is applauded by colaureates French-American economist Esther Duflo (C) and US economist Abhijit Banerjee (L) during the Award ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

King Carl XVI Gustaf of Sweden and Queen Silvia of Sweden leave at the end of the Nobel awards ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

King Carl XVI Gustaf of Sweden and Queen Silvia of Sweden leave at the end of the Nobel awards ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Queen Silvia of Sweden (L), Crown Princess Victoria of Sweden and Crown Prince Daniel of Sweden (topL) leave at the end of the Nobel Prize 2019 ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Crown Prince Daniel of Sweden (L) and Queen Silvia of Sweden leave at the end of the Nobel Prize 2019 ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Co-laureates of the 2019 Nobel Prize are congratulated at the end of the Nobel Prize 2019 ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Co-laureates of the 2019 Nobel Prize are congratulated at the end of the Nobel Prize 2019 ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)

Polish author and co-laureate of the 2018 Nobel Prize in Literature Olga Tokarczuk (C) is congratulated at the end of the Nobel Prize 2019 ceremony on December 10, 2019 at the Concert Hall in Stockholm, Sweden. (Photo by Jonathan NACKSTRAND / AFP)