Although a continued reduction in nominal average rentals has not been detected, "we are assuming that there will be a sharp change in future market rentals, a factor which is already reflected in expectations," JLL said. "All indicators point towards downward trending rentals in the future. This is only partially priced into today's yields and values... The intensity of the fall in rentals will be the crucial factor in deciding whether the market segments enter a period of relative stabilization or whether the downturn continues or intensifies."

Andrew Groom, JLL European Head of Valuation Advisory in Germany, commented: "The modest falls in values are mainly due to the weakening state of rental markets and not a broader further fall in the investment market. In spite of stumbling markets, an apparent floor for core investment properties in the prime office locations seems to be slowly forming… In an international context the German investment and rental markets are reasonably stable and, up until this point, remain relatively unscathed."

However low rental turnover may lead to falling prime and average rentals the second half which will would have a major impact on the indicator. "Until recently the full impact of the global economic crisis has not been felt in the prime office real estate markets," Groom added. "We need to see the results of the next two quarters .. In the last recession the bottom was not formed until three years after the boom ended. In today's terms that would be the middle of 2010 at the earliest."