                                                               1960  70                                                                                                                                                                                                                                                                                                                                                1.                                                          2                                                                              3                                                         4                                                                   5                                                                                                    
                                                                                                                                                                                                                                                                                             
                                                                                                                                                                                                                                                                               
                  Guyana                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  