Two years ago on this very date, the CW wrapped its sales for TV’s annual upfront market, becoming the first of the English-language broadcast networks to do so. Last year at this time, all the broadcast outlets had joined this annual fray over how much TV advertising Madison Avenue feels it should buy.

In 2015, little business has been written so far — a signal of the vast complexity that has overtaken this annual media bazaar. Advertisers are pressing for deals based on new kinds of data, and also must decide how to parcel their money among a dizzying number of media outlets, both old school and new tech. What’s more, a large number of big-spending advertisers have in recent weeks begun reviews of the agencies that handle their ad spending, which threatens to slow things down further.

“These deals have a lot of moving parts,” one media-buying executive suggested, while another noted, “There are still many advertisers without a good understanding of their budgets, which doesn’t lend itself to progress.”

Whatever the reasons, the pace of the upfront has slowed considerably from years past. In 2003, for example, the market was largely wrapped by May 23, with six English-language broadcast outlets — including the WB and UPN — securing $9.3 billion in advance advertising commitments for their primetime offerings.

“Advertisers are voting with their dollars,” Randy Falco, then a group president at NBC, told the Wall Street Journal at the time. In 2015, marketers are holding their cash much more tightly. Last year, advertisers committed between $8.17 billion and $8.94 billion for the 2014-15 primetime slate on broadcast, according to Variety estimates, compared with between $8.6 billion and $9.2 billion in 2013.

To be sure, many of the networks are engaged in substantive talks in this annual market for TV ad time. ABC has ratings growth to pitch, along with a slate of multicultural comedies. CBS has touted its 2016 broadcast of Super Bowl 50 as well as ad opportunities in its new Stephen Colbert-led “Late Show,” while Fox has talked up not only “Empire,” but the chance to buy across many sister properties, like FX. NBC has a new live variety show featuring Neil Patrick Harris that has drawn notice. The CW has called attention to its broader viewership and the success of programs like “Jane the Virgin” and “The Flash.”  And the market is prone to rev up quickly, with some buyers suggesting deals could start closing as soon as next week — if conditions are right.

There is more desire by advertisers to bench deals in new kinds of metrics. Most TV advertising sales are based on a measure known as “C3,” which looks at the viewership of commercials that accompany a program up to three days after they air, and, to a smaller extent, on “C7,” which takes into account views over the course of a week. With digital advertising, however, advertisers are able to home in on narrower swaths of audience, and they are working with nearly all the media companies to craft deals that deliver everything from first-time car buyers to consumers more prone to going to the movies.

Some of the slowdown may be due to the internal workings of the advertisers themselves. A number of big-spending advertisers — including General Mills, Coca-Cola, L’Oreal, Unilever and Johnson & Johnson — have announced reviews of their media-spending operations and the agencies that conduct them. These reviews, one buyer estimated, could affect as much as $10 billion in U.S. ad spending, and is likely to tamp down activity. Why rush to have one agency commit ad money when another one may be managing that responsibility in the future?

Another factor in the current proceedings could be more scrutiny by advertisers of Fox. In most years, Fox sparks the market, because it has fewer hours of primetime to sell than its rivals and typically attracts a younger audience than they do. Movie studios in particular often rush to reserve ad berths at the network.

In 2015, however, Fox is under pressure by advertisers to lower its pricing, owing to ratings shortfalls it has weathered in recent seasons with the aging of “American Idol.”  Because of its ratings success in past years, Fox has some of the highest rates for reaching 1,000 viewers, a measure known as a CPM that is integral to these negotiations and is used as a measure of how efficient an ad buy is in TV. Fox is under some pressure to restructure its rates, according to executives familiar with upfront talks.

Could the upfront move from talk to action in the days ahead? The answer can only be provided by the advertisers themselves.