Johannsson (I'd naturally just address him with his given name since that's customary in Icelandic but since this is a blog in English I'll obey the formalities) asks where the investment is coming from, i.e. is it coming from private enterprises or from the State. Unfortunately, distinction between private and public investments only dates back to 1997 while one can trace the aggregate investment figures back to 1945.
The first graph - sorry for the Icelandic - is the development of investment as share of GDP in Iceland back to 1945 in case of no segregation but the second shows segregated figures back to 1997.As one can see, the majority of the collapse in investment is in the private sector which one can be tempted to interpret as a symptom of a balance sheet recession.
Investment as share of GDP back to 1945. Annual aggregate numbers only available.
Segregated data of investment as % of GDP. Quarterly data back to 1Q 1997.