1910s: The music industry continues to grow, as an increasing number of Americans buy record players and listen to recorded music from their favorite musical stars.

Today: The music recording and publishing industry is threatened by the new MP3 file format, which stores music in a digital form. MP3 files can be downloaded from the Internet and played on various types of players. The Recording Industry Association of America, a music industry trade group, tries unsuccessfully to ban the use of some MP3 players.

1910s: The lives of American celebrities like Lillian Nordica become increasingly more in the spotlight. Some stars appreciate the free publicity, as it helps to boost their star power.

Today: Many public figures feel harrassed by paparazzi, a group of reporters who try to get pictures of celebrities by following them around everywhere. Diana, Princess of Wales, one of the...