Econoday's RPI provides a handy summary measure of how an economy has recently been evolving relative to market expectations.
A reading above zero means that the economy in general has been performing more strongly than expected and vice versa for a reading below zero. The closer is the value to the maximum (+100) or minimum (-100) levels, the greater is the degree to which markets have been under- or over-estimating economic activity. A zero outturn would imply that, on average, the market consensus has been correct. Note too that the index is sensitized to place extra weight upon those indicators that investors consider to be the most important.