December just started, and if history is any guide, investors have good reason to feel optimistic. It's the market's most reliable month, and certain stocks have turned the year-end period into something of a personal tradition.

Since 1950, the S&P 500 has averaged a 1.4% gain in December. More impressively, the index finishes higher 73% of the time, giving it the strongest winning rate of any month on the calendar.

Adam Turnquist, chief technical strategist for LPL Financial, noted in a Monday email that the index typically "hovers near the flatline during the first half, with upward momentum building around the 11th trading day of the month."

When December does deliver, it delivers big. In positive years, the average gain is a robust 2.9%. That compares to an average loss of 2.6% when the month turns negative.

Those seasonal patterns create interesting opportunities for specific stocks that have historically shined as the year wraps up. Looking at three decades of data, seven S&P 500 names stand out for their consistent December performance.

Cruise Lines Lead the December Rally

If you're looking for stocks with the strongest seasonal edge in December, start with cruise operators. They dominate the top of the seasonality rankings.

Carnival Corp. (CCL) has logged a 5.4% average December gain over the last 30 years. December is its best month, with a 67% winning rate. The stock's strongest December came in 1998, when shares soared 39.1%. The worst was 2022, with an 18.8% drop.

Royal Caribbean Cruises Ltd. (RCL) shows similar momentum. The stock has delivered a 4.4% average December gain over 30 years, making it the second-best month after November. It has a 57% winning rate. The best showing came in 2008 with a 46% jump, while the worst was a 23% decline in 2002.

Tech Hardware Names Show Powerful December Trends

Beyond cruise ships, tech hardware companies have carved out impressive December track records.

Western Digital Corp. (WDC) clocks a 4.66% average December gain over 30 years, with a 67% winning rate. December trails only January and November for the stock's best months. The standout year was 2001, when it surged 33.1%. The low point was a 25% drop in 2000. The stock has skyrocketed 251.7% this year.

Seagate Technology Holdings PLC (STX) has gained an average 4.2% in December since 2002. December is its strongest month after November, with a 64% winning rate. Its best December arrived in 2012 with a 21.2% gain. Its worst came this year, with a 14.8% slide.

Other December Outperformers

Mohawk Industries Inc. (MHK) enjoys its best month of the year in December. Over 30 years, it has posted a 4.1% average gain with a 60% winning rate. Its best December was 2008 with a 39.79% rally. Its worst was last year with a 14.19% decline. Shares are down 0.3% year to date.

In pharma, Eli Lilly & Co. (LLY) averages a 3.1% December gain over 30 years. December ranks as its third-best month after June and November. Its best December came in 2008 with a 17.9% rise, while its worst was a 7.3% drop in 1999.

Do Banks Join the December Party?

Two major financial institutions have shown reliable year-end gains that are worth noting.

The Goldman Sachs Group Inc. (GS) has averaged a 3% December gain since 1999. December ranks as its third-best month after October and July. Its best performance came in 2000, with a 30.2% surge. Its worst was a 13.7% drop in 2002.

JPMorgan Chase & Co. (JPM) posts a 2.5% average December gain over 30 years. December is its second-best month after October, with a 57% winning rate. Its best run occurred in 2000 with a 23.2% jump, while its worst was a 5.4% drop in 1996.

Of course, past performance doesn't guarantee future results. But when you're looking at decades of data showing consistent patterns, it's worth paying attention. December has historically been kind to the broader market, and these seven stocks have made the most of it.