Impinj is being added to the S&P small-cap index. Shares of Impinj (PI 9.10%) were moving higher today on news that the company was joining the S&P SmallCap 600 after S&P Global made its quarterly rebalancing announcement Friday afternoon. As a result, Impinj stock was trading higher by 10% as of 2:03 p.m. ET on Monday. Impinj gets a stamp of approval The announcement from the S&P was the latest sign that Impinj's recent growth is here to stay as the specialist in RAIN RFID tags, which allow the tracing of ...