What happened Shares of Lattice Semiconductor (NASDAQ: LSCC) soared today, up by 13% as of 1:40 p.m. EDT, after S&P Dow Jones Indices announced that the company would be joining the S&P MidCap 400 index. While the news has no bearing on Lattice's business fundamentals, it does create buying activity from index funds that track the underlying index, which are now obligated to purchase the stock. So what The dominant index provider is shuffling constituents for three different widely followed indexes, the S&P 500, the S&P MidCap 400, and the S&P SmallCap 600, all of which will become effective on Tuesday, April 20. Image source: Getty Images. In the S&P 500, PTC will be replacing Varian Medical Systems since Siemens just closed its acquisition of Varian Medical Systems and it is no longer a publicly traded stock. For the S&P MidCap 400, PTC and Domtar are being removed while Lattice Semiconductor and Progyny will be added to the mix. Domtar will take NIC's place in the S&P SmallCap 600. Now what As mentioned, index changes have no bearing on a company's business or financial performance, but typically trigger buying and selling activity as funds rebalance their portfolios. Lattice shares have hit all-time highs on heavy volume as those funds start accumulating positions ahead of the effective date. Lattice is scheduled to report first-quarter earnings on May 4 and expects revenue to be in the range of $106 million to $114 million. Analysts are forecasting $110.1 million in sales. 10 stocks we like better than Lattice SemiconductorWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Lattice Semiconductor wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Evan Niu, CFA has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends NIC. The Motley Fool recommends PTC. The Motley Fool has a disclosure policy.Source