Violent crime, gun crime, murder rates.

What other kinds of crime are there, and how would you measure how much of it there is?

What other kinds of crime are there due to which we're willing to give up our right to privacy? Several, perhaps, but remember that this conversation is happening while we're discussing a way in which too much law enforcement has significant downsides to a free and happy society. We wouldn't let the government monitor everyone constantly in order to catch shoplifters.

I suspect that the FBI antipathy to encryption, if it's not fundamentally irrational, is actually about white collar crimes: trade secrets theft, money laundering, insider trading, tax evasion... Violent crime leaves abundant physical traces. White collar crimes may sometimes be un-prosecutable or even undetectable without access to electronic records.

They know that "outlaw secure encryption to stop inside traders" is going to be an even tougher sell than "outlaw secure encryption to stop murderers," so they try to make an illogical argument involving scary criminals instead of a stronger argument with not-scary criminals.

My first guess, when I posed the original question, was organized crime. People who do organized crime would be the ones to benefit the most from encrypted phones. But anecdotally, it seems to me that organized crime is down in the U.S. too. I might be wrong, that's why I asked for evidence.

The white collar crime, yeah, some forms of it might benefit from encrypted communication. But again, where is the evidence? Is the tax evasion (non-institutionalized) skyrocketing?

The whole claim is just very suspicious. I think there is so much open data today that even with encrypted phones it's much harder to leave less trace than in the past.

I too suspect that the FBI's antipathy to encryption is disproportionate to how much it actually hinders law enforcement. But if there were some real reason for the FBI to be this hostile to encryption, I don't think it can be about violent crimes. It has to be more subtle crimes that don't leave physical evidence.

How many bankers have gone to jail for crashing the US economy?

The FBI doesn't give a shit as long as it's the anus of the average citizen being ravaged. They only care when it's against the 1%.

This would be more plausible if federal prosecutors ever prosecuted "white collar" crime in general, rather than only in particular situations to defend the commercial interests of big donors. To see this, look at how many insider trading investigations are targeted at randoms who occasionally learn some privileged information, compared to those targeted at senior executives who bathe in it all day long. The ratio of bitcoin convicts to great recession convicts is still infinite.

Property crime is also down to around the rate of the mid 1960s.

http://www.wolframalpha.com/input/?i=property+crime+rate

Fraud is probably greatly increased.

Fraud has largely moved outside of the US as Fraud takes a lot of legwork.

In the 60's you also got a lot more check fraud. Which is similar to CC fraud, but that's again for more global.

Opinion or rational deduction from evidence?

Well, people tend to still report other crimes, like property crime, and police still investigate them. Sure, reporting rates aren't perfect but you can still draw meaningful conclusions from trends. I'm not going to do the leg work for you, but almost all types of crime are declining in the US and have been for decades.

There's no data I've seen that suggest anything other than a broad decades long drop in crime.

If “attempting to access a computer system without authorisation” counts, a former aquaintance reported over 24k such attempts per day. Against just his private server.

While I count all attacks from a single process to be “one attack” and “one crime”, others may not.

Then there’s “unlawful pornography”, which varies wildly by jurisdiction — when a friend pointed me at fetlife, one of my thoughts was that the entire site is illegal to view in the UK unless you disable images (I’m no lawyer though).

There are probably a lot of other things describable as “conspiracy to X”, but that’s a guess on my part.

(I think there may be a lot of victimless crimes too, but that’s a different topic).

There's white collar crime. There's several non-violent variations on theft. Loan sharking isn't violent per se (though usually comes with an unhealthy side order of violent crime).