"Index funds can help investors achieve long-term success through their low costs, broad diversification, low turnover and relative predictability," Comegys says. To further diversify a U.S.-heavy stock portfolio, Vanguard offers VTIAX for broad exposure to a wide swath of international stocks.

Shares of Firefly Aerospace ( FLY +3.40%) shot up 26.3% in December, according to data from S&P Global Market Intelligence. The stock is performing well due to recent bullish sentiment surrounding space stocks, specifically in anticipation of a potential SpaceX IPO, as well as its inclusion in new stock indices.

The CAPE (cyclically adjusted price-to-earnings) ratio measures how expensive the stock market is relative to how much companies are earning. The heuristic works as a reality check: When CAPE is high, stocks are richly priced and future returns have been historically lower. When CAPE is low, stocks tend to be cheaper.

The Shiller P/E ratio passed a mark on Monday it last hit during the dot-com bubble. The stock-market indicator peaked before the S&P 500 crashed 49% in the early 2000s. AJ Bell's Russ Mould said stocks are pricey, but "you don't know when trouble is going ...

Stock index futures pointed to a higher open Monday with the traditional Santa Claus Rally period starting midweek. Nasdaq 100 futures (US100:IND) advanced +0.75%. S&P 500 futures (SPX) rose +0.52% and Dow futures (INDU) edged higher by +0.18%. The Santa ...

SanDisk was the top performing S&P 500 stock in 2025. Citi believes SNDK shares will push higher still this year.