Yarn is basic raw material for power loom sector and the increasing nylon and polyester yarn prices has destabilized the sector further which is reeling under the after-effects of implementation of Goods and Services Tax (GST), despite the fact that GST Council had reduced GST on yarn from 18 per cent to 12 per cent. The rally of yarn prices is going on since September, said Pandesara Weavers Cooperative Society President Ashish Gujarati.