Final answer:
About 15 percent of infants worldwide receive daily care from grandparents, who often take over as primary caregivers due to various issues such as parental drug abuse or abandonment.
Step-by-step explanation:
Worldwide, only about 15 percent of infants receive daily care from grandparents. This is due to a variety of family structures, where sometimes a parent may not be present. In cases such as parental drug abuse, incarceration, or abandonment, grandparents often step in as primary care providers. In 2010, statistics showed that 54 percent of children living with a guardian who was neither their biological nor adoptive parent lived with grandparents. It is significant to note that a grandparent providing primary care can be a long-term arrangement brought on by various factors such as the parent's inability to care for their child.