URBANA — The University of Illinois Flash Index moved higher in May, showing slow but continued economic improvement in the state.

The index, a key indicator of economic activity in Illinois, climbed to 96.8 in May, up two-tenths of a point from April.

This marked the 13th time in the last 14 months that the index has risen. Nevertheless, it remains below 100, which marks the division between economic decline and economic growth in the state.

"The increase in the Flash Index has mirrored a decline in the state's unemployment rate over the past 12 months," said UI economist J. Fred Giertz, who compiles the Flash Index for the university's Institute of Government and Public Affairs. "At 8.7 percent in April, the rate had fallen below the national unemployment rate, which stood at 9 percent. This is an unusual occurrence since the Illinois rate has exceeded the national rate for most months over the past two decades."

The low point for the index in recent years was 90, which was reached in September 2009. Before the recession, the Flash Index set a high of 107.4 in April 2007.

According to Giertz, after adjusting for the individual and corporate income tax rate increases earlier this year, all three components of the index (the sales tax, the individual income tax and the corporate tax) were all up in real terms compared with the same month a year ago.

The Flash Index is a weighted average of Illinois growth rates in corporate earnings, consumer spending and personal income. Tax receipts from corporate income, personal income and retail sales are adjusted for inflation before growth rates are calculated. The growth rate for each component is then calculated for the 12-month period using data through May 31, 2011.