Datasets:
| Year,Nigeria,Romania,Dominican Republic | |
| 1960,6.364,2.34,7.555 | |
| 1964,6.362,1.96,7.186 | |
| 1969,6.438,3.19,6.366 | |
| 1973,6.633,2.44,5.667 | |
| 1978,6.921,2.52,4.644 | |
| 1982,6.799,2.17,4.014 | |
| 1987,6.504,2.38,3.528 | |
| 1991,6.426,1.59,3.349 | |
| 1996,6.217,1.3,3.04 | |
| 2000,6.124,1.31,2.869 | |
| 2005,6.063,1.4,2.574 | |
| 2009,5.993,1.66,2.574 | |
| 2014,5.622,1.56,2.451 | |
| 2018,5.021,1.76,2.397 | |
| 2023,4.482,1.71,2.243 | |