Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
|  | Average population (x 1000) | Live births | Deaths | Natural change | Crude birth rate (per 1000) | Crude death rate (per 1000) | Natural change (per 1000) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 1970 | 31 | 683 | 356 | 327 | 22.0 | 11.5 | 10.5 |
| 1975 | 33 | 706 | 374 | 332 | 21.4 | 11.3 | 10.1 |
| 1980 | 35 | 701 | 351 | 350 | 20.0 | 10.0 | 10.0 |
| 1985 | 37 | 793 | 289 | 504 | 21.4 | 7.8 | 13.6 |
| 1990 | 38 | 635 | 342 | 293 | 16.9 | 9.1 | 7.8 |
| 1991 | 38 | 623 | 350 | 273 | 16.6 | 9.3 | 7.3 |
| 1992 | 37 | 611 | 369 | 242 | 16.7 | 10.1 | 6.6 |
| 1993 | 34 | 459 | 433 | 26 | 13.3 | 12.6 | 0.8 |
| 1994 | 32 | 433 | 460 | - 27 | 13.5 | 14.3 | -0.8 |
| 1995 | 31 | 382 | 481 | - 99 | 12.5 | 15.8 | -3.2 |
| 1996 | 29 | 374 | 436 | - 62 | 12.7 | 14.8 | -2.1 |
| 1997 | 29 | 373 | 400 | - 27 | 13.0 | 13.9 | -0.9 |
| 1998 | 28 | 396 | 355 | 41 | 14.2 | 12.7 | 1.5 |
| 1999 | 27 | 319 | 397 | - 78 | 11.8 | 14.7 | -2.9 |
| 2000 | 26 | 289 | 391 | - 102 | 11.0 | 14.9 | -3.9 |
| 2001 | 26 | 298 | 390 | - 92 | 11.6 | 15.1 | -3.6 |
| 2002 | 25 | 310 | 376 | - 66 | 12.3 | 14.9 | -2.6 |
| 2003 | 24 | 268 | 462 | - 194 | 11.0 | 19.0 | -8.0 |
| 2004 | 24 | 339 | 463 | - 124 | 14.4 | 19.7 | -5.3 |
| 2005 | 23 | 294 | 466 | - 172 | 12.9 | 20.5 | -7.6 |
| 2006 | 22 | 270 | 366 | - 96 | 12.3 | 16.7 | -4.4 |
| 2007 | 21 | 280 | 351 | - 71 | 13.2 | 16.5 | -3.3 |
| 2008 | 20 | 267 | 368 | - 101 | 13.0 | 18.0 | -4.9 |
| 2009 | 20 | 268 | 365 | - 97 | 13.6 | 18.5 | -4.9 |
| 2010 | 19 | 233 | 397 | - 164 | 12.3 | 20.9 | -8.7 |
Question:
how many years span the table entry?
Answer:
40