• by David Goetzl  @dgoetzl, April 1, 2008

As the writers' strike caused upheaval early this year, the average cost of a prime-time spot dropped 12%, while even "American Idol" couldn't prevent a notable slide at Fox.

For the Big Four networks, the average spot in the first quarter--melding prices from the upfront and scatter markets--cost $125,634. That's compared to $142,824 a year ago, accounting for the 12% decrease, according to a new report.

The research comes from independent media agency TargetCast tcm, which culled the data from NetCosts, a service run by SQAD that receives reports on spending from some 390 advertisers and agencies. (SQAD says NetCosts represents 40% of all national TV ad expenditures in the $42.8 billion U.S. market.)

Looking at individual networks in the first quarter, Fox saw its average unit cost drop 9.2% to $237,237. That's more than double CBS ($112,641); nearly double ABC ($122,509); and more than three times as high as NBC's $77,893. The figures do include the Super Bowl, which aired Feb. 5 on Fox.

In percentage terms, Fox was down the least in the first quarter versus 2007, followed by ABC at a 9.5% decrease. CBS fell 11.9%, and NBC dropped 24.7%.

With the writers' strike running through mid-February, networks were left without new episodes of scripted hits, such as "Grey's Anatomy" and "CSI," leading to double-digit ratings drops in the first quarter.

Those ratings dips, in turn, led to networks having to dole out makegoods, which caused a spike in scatter prices so severe that marketers opted to shift dollars elsewhere. That prompted a trickle-down effect contributing to the drop in unit pricing, according to TargetCast findings.

"Clearly, the writers' strike caused uncertainty with viewers and advertisers, which impacted ratings and actual prices paid," said Gary Carr, senior vice president, director of broadcast services at TargetCast.

Before fresh scripted fare was in short supply, networks were able to post moderate pricing increases last fall. Advertisers have no options to pull out of their upfront commitments in the fourth quarter. The increases were likely due to the strong upfront pricing several months before. The increases came even as ratings were down significantly in the fourth quarter (save Fox).

In the October through December period, ABC saw its average unit price increase 7.3% to $159,008 -- both marketplace highs. Fox and CBS had near-parity pricing at $139,529 and $139,414, good for respective year-over-year increases of 1.5% and .4%. NBC saw a notable percentage increase--up 3.4%--but still lagged in average unit cost at $121,314.