## 7.5 Models

$$Y_t = T_t + S_t + C_t + R_t$$
• $$C_t$$ and $$S_t$$ can be $$\pm$$ve
• $$R_t$$ can also be $$\pm$$ve, but in the long run, $$\sum R_t = 0$$
• $$Y_t = T_t \times S_t \times C_t \times R_t$$
• $$S_t, C_t, R_t$$ refer to deviation from unit
• $$S_t$$ equals unity in 1 year, $$C_t$$ in a cycle, and GM of $$R_t$$ is unity (1).