Before revision: This paper considers price volatility as the reason for description of the second-degree economic variables, trades and expectations } } aggregated during certain time interval {\Delta}.
After revision: This paper considers price volatility as the reason for description of the second-degree economic variables, trades and expectations }(p;t) that defines the mean price p(1;t), mean square price p(2;t), price volatility } aggregated during certain time interval {\Delta}.