March 14 (Bloomberg) -- Commodities may have ``explosive rallies'' in the next couple of years, with crude oil rising to $175 a barrel, according to Goldman Sachs Group Inc.

Political decisions on money flows, labor and technology are ``substantially constraining supply growth'' of commodities, Goldman analysts including Jeffrey Currie in London wrote in a report today. ``This will likely support the ongoing structural bull market in commodities until these policy-driven investment constraints are removed and/or demand is adjusted.''

Commodities are in their seventh year of gains as underinvestment in refineries, mines and land sent prices for oil, gold, platinum and wheat to records. More natural resources are controlled by political entities than at any time since the 17th century, according to the Goldman report.