SHANGHAI, May 8 (SMM) - Last week, the weekly average discount of high-grade NPI stood at 820 yuan/mtu against refined nickel, 17 yuan/mtu narrower than two weeks ago. In terms of refined nickel, the nickel prices were on a downward trend last week as the prices moved abnormally earlier affected by the futures prices. The NPI traded prices rose somewhat since the stainless steel mills raised the purchase prices and the NPI suppliers quoted higher NPI prices after the Labour Day holiday. The stainless steel sector may exert some pressure on NPI prices due to poor stainless steel consumption. What's more, influenced by US non-farm data, the overnight nonferrous metals prices rose last Friday, while the NPI prices would experience some declines. The discounts of high-grade NPI against pure nickel will thus expand further.