Here are significant figures and why they matter. History of Negros (1980) illustrates:
Sugar production (in Negros) increased from 3,000 piculs in 1850 to 14,500 in 1856 and 40,000 in 1861.
In the beginning, almost all of the sugar produced by Negros was sent directly to Manila as Ilongo sugar. The rest was sent to Iloilo where it was reshipped to Manila as Ilongo sugar.
However from 1856 a change occurred. The shipments to Iloilo constantly increased while the shipments to Manila did not increase and even tended to decrease although they never completely disappeared.
Dumaguete never ceased sending to Manila a part of its production. The high prices paid for sugar, abaca, bayongs, coconut oil and other local products allowed shippers to meet the costs of transportation and still make a profit. In 1862 inter-island vessels carried to Manila 12,272 piculs of Negros sugar and in 1863, 12,474.
The lack of confidence on the part of foreign merchants in Manila, the opposition of local shipping companies who were interested in inter-island shipping and the poor harvests of 1856, 1857 and 1858 delayed for a few years the beginning of exports from Iloilo.
There was a customs house there (in Iloilo) since 1855 but it was inactive since all produce intended for export was first sent to Manila. In 1855, Iloilo sent to Manila 752 tons of sugar; in 1856, 850; in 1857, 1800 and in 1858, 1,290. A part of these shipments came from Negros although we cannot tell precisely how much except for that of 1855: 189 tons.