Table:
| As of December 31, |  |  |
| --- | --- | --- |
|  | 2018 | 2019 |
|  | NT$ | NT$ |
|  | (In Thousands) | (In Thousands) |
| Raw materials | $3,766,056 | $5,102,571 |
| Supplies and spare parts | 3,133,737 | 3,548,376 |
| Work in process | 10,034,488 | 11,309,718 |
| Finished goods | 1,268,838 | 1,754,137 |
| Total | $18,203,119 | $21,714,802 |
Paragraphs:
a. For the years ended December 31, 2017, 2018 and 2019, the Company recognized NT$118,252 million, NT$123,795 million and NT$122,999 million, respectively, in operating costs, of which NT$2,256 million, NT$1,698 million and NT$820 million in 2017, 2018 and 2019, respectively, were related to write-down of inventories.
b. None of the aforementioned inventories were pledged.
Question:
What was the increase / (decrease) in the raw materials from 2018 to 2019?
Answer: 5102571 - 3766056 = 1336515