In the strange year of 1999, when the total number of events dropped from 21 to 16, there were no five-card events. That's the only time that has happened.
Note: Mixed Games are considered "Other" for most sections of this series of articles.
Draw and Stud games, as opposed to Flop games, were more prevalent in the early days. Draw games peaked at 29% of events (2 of 7) in 1973. They've been in single-digit percentages since 1993, with 7% in 2016.
Stud games peaked at 53% of events (7 of 13) in 1977, have been in single-digit percentages since 2008, and were coincidentally also 7% in 2016.
Flop games started at 20% of events (1 of 5), reached 50% in 1989, and had crept up to 67% by 2003. When Chris Moneymaker won the Main Event though, the WSOP responded by greatly increasing the number of No-Limit Hold 'Em events, the game most popular among the wave of new players. Flop games peaked at 87% (40 of 46) in 2006 before dropping to 75% (41 of 55) in 2007. The percentage dropped to 71% (49 of 69) in 2016, the lowest since 2003.2
The online 2020 WSOP had nothing but flop games, with 71 Hold 'Em and 14 Omaha tournaments.
Mixed games debuted in 2000 and have slowly but surely increased since 2007 from 9% (5 of 55) to 14% (10 of 69) in 2016.
Every event in the online 2020 WSOP was high-only.
Hi/Lo events debuted in 1976, surpassed Low events in 1995, and peaked at 21% in 2000 before sinking back to 9% in 2015 and 10% in 2016.
Limit poker dominated the early days of the WSOP. Initially only the championship event was no-limit. Although no-limit games briefly took over in 1975 (60%) and 1976 (63%), limit games were otherwise the majority of the events until 2000. From 2001 to 2004, limit still held the lead but had fallen under 50%. With the Moneymaker effect, however, No-Limit Hold 'Em alone pushed no-limit games ahead to stay in 2005 (48%), accounting for over half the events since 2008 (54% in 2016).In 1984, a year after Omaha debuted as a limit game, it became the first pot-limit event at the WSOP. Pot-Limit Hold 'Em could have been played much sooner but didn't appear until 1992, two years after the first Pot-Limit Omaha 8 event.4
Why is Omaha usually played pot-limit, while Hold 'Em is usually no-limit? Because draws are much more prevalent and can have much better odds in Omaha. In No-Limit Omaha, players would frequently be correct to move all-in, or at least bet much more than the pot size, to give improper draw odds. Shovefests lower the better skilled player's advantage.
The online 2020 WSOP was an exception to this trend with 14 Pot-Limit Omaha out of 85 events.