TripAdvisor announced today that it reached a 150-million review milestone earlier this month.

One-third of the total reviews were posted in 2013 alone and their rapid growth, a 50 percent year-over-year increase, highlights the popularity of and growing reliance on user-generated content in the travel planning process.

TripAdvisor currently has more than 60 million members worldwide, a combination of prolific contributors and quiet onlookers. The site revealed that 24,710 TripAdvisor members, less than 0.05 percent, have contributed more than 100 reviews.

A company spokesperson would not reveal any additional details on the average number of reviews written by each member.

A TripAdvisor-commissioned study found that more than half of respondents worldwide want to look at reviews before booking a hotel. And that 80 percent of respondents read 6 to 12 reviews before making a decision.

Photo Credit: TripAdvisor's website redesign, unveiled in late 2013, is seen on the computer screen above. TripAdvisor