Final answer:
The incorrect statement is that 'economists have not been able to isolate the RBC theory impulse.' In real business cycle theory, productivity fluctuations correlated with GDP fluctuations are mainly attributed to technological changes, and these impulses have been studied and measured by economists. The correct answer is option c.
Step-by-step explanation:
The statement about real business cycle (RBC) theory that is incorrect is: c. economists have not been able to isolate the RBC theory impulse. RBC theory posits that productivity fluctuations are indeed correlated with real GDP fluctuations and these can often be traced to technological changes. The impulse in RBC theory is primarily a result of exogenous technological innovations, which means it is something that economists can and have attempted to measure and identify.
The growth rate of productivity resulting from technological change is a central element of RBC theory. RBC assumes that the economy experiences real fluctuations in output due to technological innovations, that these innovations drive productivity, and thus influence the business cycle. Hence, while research and development can be important for technological progress, it is the technological change itself, which may arise from various sources, and not just the process of research and development that plays a key role in generating the RBC impulse.