| Year | Real Values | Predictive Values | Error (%) |
| 1961 | 1.692 | 1.692 | 0 |
| 1965 | 1.874 | 1.832 | −2.235 |
| 1970 | 2.117 | 1.894 | −10.514 |
| 1975 | 2.165 | 1.914 | −11.578 |
| 1980 | 2.262 | 1.965 | −13.124 |
| 1985 | 2.188 | 2.019 | −7.741 |
| 1990 | 2.243 | 2.018 | −10.045 |
| 1995 | 2.198 | 2.029 | −7.669 |
| 2000 | 2.196 | 2.234 | 1.728 |
| 2001 | 2.190 | 2.278 | 4.007 |
| 2002 | 2.2 | 2.330 | 5.909 |
| 2003 | 2.23 | 2.381 | 6.771 |