  We suggest use continuous numerical risk grades [0,1] of R for a single risk
or the unit cube in Rn for n risks as the economic domain. We consider risk
ratings of economic agents as their coordinates in the economic domain.
Economic activity of agents, economic or other factors change agents risk
ratings and that cause motion of agents in the economic domain. Aggregations of
variables and transactions of individual agents in small volume of economic
domain establish the continuous economic media approximation that describes
collective variables, transactions and their flows in the economic domain as
functions of risk coordinates. Any economic variable A(t,x) defines mean risk
XA(t) as risk weighted by economic variable A(t,x). Collective flows of
economic variables in bounded economic domain fluctuate from secure to risky
area and back. These fluctuations of flows cause time oscillations of
macroeconomic variables A(t) and their mean risks XA(t) in economic domain and
are the origin of any business and credit cycles. We derive equations that
describe evolution of collective variables, transactions and their flows in the
economic domain. As illustration we present simple self-consistent equations of
supply-demand cycles that describe fluctuations of supply, demand and their
mean risks.
