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 Even though there is little practical use for heavy horses today because their muscle power has been replaced by machinery, breeders and enthusiasts have ensured that the breed is increasing, rather diminishing in numbers.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).
With about 1,049 male babies born for every 1,000 female babies born in 2013, boys are keeping the edge in a ratio that's stayed about the same over the past 60 years. Twins. The number of twins born in the United States increased 2 percent in 2013 â to 33.7 sets of twins born for every 1,000 births. While this is the highest rate on record, the numbers have remained roughly the same since 2009 â after skyrocketing over 70 percent from 1980 to 2008.