Re: Protection from what?
"Scandinavia ..... They tended to start sexual relationships later than the UK or USA."
Same here in NL (though I haven't come across that much porn in the newsagents here). Teenage pregnancies lowest in the EU, 3.2 per thousand (UK: 14.4). Source: CBS/Statistics Netherlands, 2015 data, quoted in https://www.volkskrant.nl/mensen/aantal-tienermoeders-blijft-dalen-nederlands-percentage-laagste-in-eu~ba6ac1ea/).
I also seem to remember reading an article which indicated that the age at which 50% of the population had had sex was around 18 years which I gather is also relatively late.