A key challenge to any community-wide audience-building initiative is the lack of effective metrics. If you don't have a benchmark when you begin, it's hard to know if all of your messaging, discounts, web sites, and innovative practices have had any positive effect on the thing you intended to improve.

The Greater Philadelphia Cultural Alliance is attempting to resolve that challenge through its Cultural Engagement Index, announced this month (here's the press release). The index, as its name implies, is a baseline measure of cultural engagement -- broadly defined -- that can be measured against over time.

While a few survey projects have sought to gather audience participation data over time (most notably, the Survey of Public Participation in the Arts gathered through the U.S. Census), this attempt is unique in a number of ways:

• It explores "cultural engagement'' rather than the more limited ''arts participation,'' which includes both traditional audience participation and personal practice in arts and culture.
  
• It measures not only frequency of participation, but perceived importance or ''salience,'' adding depth and meaning to simple headcounts.
• It drills down to discover basic goals or drivers that inform cultural engagement, which can then be assessed by demographic segment.

The index is designed to be measured every few years, to mark changes in key elements over time. Thanks to the Greater Philadelphia Cultural Alliance, who commissioned the initiative, and WolfBrown, who designed it, we all will get to follow along on what they discover.