Meet the Clydesdale. The Clydesdale breed once almost faced extinction. Even though there is little practical use for heavy horses today because their muscle power has been replaced by machinery, breeders and enthusiasts have ensured that the breed is increasing, rather diminishing in numbers.
1 Over the three decades, the twin birth rate rose by 76 percent, from 18.9 to 33.2 per 1,000 births (or from 1.9 percent to 3.3 percent of all births) (Figure 1). 2  Increases in the twin birth rate averaged more than 2 percent a year from 1980 through 2004 (peaking at more than 4 percent from 1995 to 1998).
Best Answer: Population biologists have estimated that maintenance of human population requires at least 1.6% birth rate per year. In the US, there are about 4 million live births per year, or roughly 1.3%; this alone would lead to negative population growth if not for immigration. Worldwide population increases by about 2% per year, so the worldwide birth rate must be roughly 3.5%, or 210,000,000 annually. There are 31,556,736 seconds in a year (60 X 60 X 24 X 365.24). Rounding off a little for convenience (and because babies don't come in fractions), that comes out to about 7 per second.