One eye-popping number shows why there were so many car ads during the Olympics

If it felt like nearly every ad was a car ad during NBC's Olympics broadcasts, you're not far off.

The industry spent more than $159.5 million on TV advertising during the games - more than any other sector, according to iSpot.tv, which tracks and estimates television ad spending.

Four of the top-10 advertisers were auto-makers. And the top spender overall was auto insurer GEICO.

Chevrolet, BMW, Ford, and Toyota were the top auto advertisers, and iSpot reports the industry as a whole ran 89 spots nearly 1500 times during the games.

GEICO, already ubiquitous on television, is estimated to have spent more than $45 million running five ads during the Rio Olympics, including this one with Marco Polo playing a game of Marco Polo.

BMW had a whopping 12 different spots on TV, which it paid $37.5 million to run, but it was outspent by Chevrolet. GM invested nearly $41 million to air the four Chevy spots.

The only advertiser to get more airtime was NBC itself, which broadcast the games. And its parent company, Comcast, used the big audience to promote its brand.

iSpot's data comes from tracking TV ads as they run on television, and from 11 million set-top boxes it uses to measure whether viewers are watching the ads.

But ratings for NBC's Olympics coverage fell short of expectations - down from its 2012 London broadcasts by about 17%. Anthony Crupi at AdAge reports those declines mean NBC may have to offer "make-goods" to compensate companies whose ads were not seen by the number of people the network promised. Some may get free spots during upcoming football games.