Interesting information regarding the production and sale of fireworks from the Progressive Policy Institute:

Dr. Joseph Needham, eminent British historian of Chinese science,
traced fireworks back to an origin sometime in the Sui or early Tang
dynasty, meaning around 650-700 AD. Chinese legend, or history, has
a roughly similar date and also a name: a Hunan farmer (or,
alternatively, monk) named Li Tian gets credit for inventing the
firecracker.

A millennium and a half later, tomorrow's Independence Day
celebrations will feature about 250 million pounds of fireworks.
Macy's 4th of July Fireworks in New York, biggest by tonnage, will
set off more than 30,000 fireworks shells and over 40,000 pounds of explosives. Boston's Pops Fireworks Spectacular and Washington's Independence Day Celebration are not far behind at 20,000 pounds apiece. Big shows like these cost nearly half a million dollars, and the American appetite for pyrotechnics has been growing fast. (Annual use of fireworks has jumped from 34,000 tons in 1990 to 140,000 in 2006.) So the pyrotechnic business is healthy, with industry earnings nearly tripling from $350 million to $900 million since 1997.

Fireworks show producers in the United States are mostly family-
owned American firms: big ones include Zambelli and Pyrotecnico of
New Castle, Pa., both founded by Italian immigrants in the late
1800s; California's equally venerable Pyro Spectaculars, owned by
the Souza family; and relative newcomer Pyro Shows of Tennessee.
Zambelli and some others are also large-scale fireworks
manufacturers; but today, as it was in the Tang era, China is the
world's pyrotechnical center.

Whatever the facts about Inventor Li, his hometown -- Liuyang, in
Hunan province -- now has 1,500 fireworks factories, and claims to
make about half the world's sparklers, firecrackers, bottle-rockets,
and higher-value display fireworks. (Though Guangdong and Guangxi argue the point, and the Chinese Customs Service credits Hunan with only about 40 percent of China's fireworks exports.) Much of this output will go to tomorrow's celebrations: About 95 percent of the United States' 123,000 tons of fireworks imports last year, twice the figure for the 1999 run-up to the millennial celebration -- came from China. (The bill was $206 million; for its part, the Chinese Customs Service reports 651.2 million pounds of fireworks exports last year, valued at $402 million.) American fireworks manufacturers, though, sell abroad as well: U.S. firms sold about $22 million of high-end fireworks abroad, with Canada, Japan, the Caribbean islands, and China itself as the big buyers.