Those remittances are Mexico's second largest source of foreign revenue, after oil.
For people under 35, student loans are the second largest source of debt behind mortgages.
India is Australia's second largest source of international students and third largest trade partner, behind the US and China.
For years, the United States has pressed Peru, the second largest source of cocaine, after Colombia, to fight production of the drug.
Add to this that the main employer is the United States government, and that the second largest source of jobs is Tyson Foods, in Arkansas.
Spotify is the second largest source of digital music revenue for labels in Europe, according to the International Federation of the Phonographic Industry IFPII).
China had become Tanzania's largest trading partner and its second largest source of investment; bilateral trade had reached $2.47 billion in 2012, up 15.2% from the previous year.
The business tax is the city's second largest source of revenue, after property tax, but tends to fluctuate dramatically, says the nonprofit San Francisco Planning and Urban Research Association.
"The best case scenario is continued research into alternate cleaner uses of brown coal so we can establish manufacturing or processing industry around what is Australia's second largest source of energy, which is Victoria's largest source of energy.
According to children's charity Unicef, 1.2 million youngsters are trafficked every year and human trafficking is said to be the second largest source of illegal income worldwide, exceeded only by drug trafficking.
