What's the secret to making a hit track these days?

What do all high-ranking songs have in common these days? According to a recent episode of MBC's 'This Morning', short opening instrumentals provide a quick entry to the song; this principle has been dubbed as the "30 second rule".   Examples include 2PM's "Hands Up", f(x)'s "Hot Summer", SECRET's "Starlight Moonlight," and CSJH's Dana and Sunday's "One More Chance". The CSJH duo shared, "We wanted the focus to be on the lyrics, so there is a very short introduction to our song." A music critic explained, "Since internet previews only let you hear the first thirty seconds, the opening instrumentals in these new songs are getting shorter and shorter." Of course, jumping right into the lyrics doesn't guarantee a hit track, but it's interesting to note how technology is affecting how songs are being structured. Source: Korea Economic Daily via Nate