Worldwide, the screen advertising industry was worth $1.3 bln in 2003. While it only represents on average 0.9% of total display advertising, it is considered a vital plank in many cross and single-media campaigns, according to ScreenDigest. Screen advertising revenues as a proportion of box office is a good indicator of the sector's state of maturity and relative importance. Over all the territories covered, the average proportion was 12.9% in 2003. This is an increase on the previous two years. There is a wide range in this measure across all territories. The highest proportion is in the UK, where screen advertising constitutes 24.3% of gross box office, although screen advertising revenue figure also includes production and sponsorship, raising the figure artificially.