The streaming giant fell short on viewership for its new ad-supported platform.

Among the biggest losers in last week's selloff were Netflix and other streaming stocks. NFLX shares fell 9% on December 15 following reports the streaming giant is falling short on viewership guarantees it made to advertisers for its new ad-supported streaming service. Shares are 1% higher in early trading Friday.

Investors had been counting on the new ad tier to draw a substantial audience, but the company reportedly delivered only around 80% of its expected audience.

The poor performance could mean Netflix may have to lower its ad prices. It had been seeking a relatively high $55 cost per thousand impressions (CPM), above the $50 CPM of Disney+. Advertisers are also faulting Netflix for not pushing its own market campaign for the ad-supported tier.

Netflix shares had climbed about 67% over the past six months, but are still down about 51% so far this year. Warner Bros. Discovery (WBD) and Paramount Global (PARA) shares also fell about 9% yesterday. Disney's (DIS) stock price was down about 4%.