My grandmother used to say, "figures lie and liars figure."
Was there evidence that crime was on the rise? Yes. Was there evidence that crime was declining? Yes.
The Senate's 1950 report on Juvenile Delinquency is a good place to start when looking for an answer to this question, The report is full of responses that had been solicited from all sorts of public officials around the country. The Senators asked these (very leading) questions of the officials:
1) Has juvenile delinquency increased in the years 1945 to 1950? If you can support this with specific statistics, please do so.
2) To what do you attribute this increase if you have stated there was an increase.
3) Was there an increase in juvenile delinquency after World War I?
4) In recent years have juveniles tended to commit more violent crimes, such as assault, rape, murder, and gang activities?
5) Do you believe that there is any relationship between reading crime comic books and juvenile delinquency?
6) Please specifically give statistics and, if possible, state specific cases of juvenile crime which you believe can be traced to reading crime comic books.
7) Do you believe that juvenile delinquency would decrease if crime comic books were not readily available to children?
The letter from the Committee was dated August 8, 1950, and responses were expected by August 22, 1950, so I expect many agencies had to scramble (in the pre-computer era) to obtain data for their responses. Despite the fact that the questions were obviously worded so as to elicit a response of "juvenile crime is increasing, and comic books are the cause," the responses can hardly be tallied as overwhelming evidence of an increased crime rate or of the dangers of comic books.
In response to this questionnaire, here are selections from just the first few responses in the report:
From J. Edgar Hoover, director of the FBI, "Arrests of youths have generally leveled off during the postwar period (1945-49) although the incidence of crime among young people is still abnormally high." He does not state what is meant by "abnormally high," and his statistics don't seem to back up this statement. He goes on to cite specific increases and decreases, and then states, "it should be noted that arrests of boys and girls under 21 in 1949 were 3 percent higher than in 1945."
Up 3%. Yup, that sounds like an increase to me. However, Hoover does not state that his figures are per capita, and provides a chart that is clearly absolute arrests and not per capita arrests. Looking at census bureau figures for those years (http://www.npg.org/facts/us_historical_pops.htm) it appears to me that the population grew by about 8% from 1945 to 1949. So in reality, this would be a per capita DEcrease in crime.
Hoover goes on to state that "The basic cause of the high rate of juvenile crime is the lack of a sense of moral resonsibility among youth."
Next we have a letter from A.H. Conner, Acting Director, Federal Bureau of Prisons, "Dispositions of juvenile cases by Federal courts rose steadly beteen the years ending June 30, 1941 and June 30, 1946, but since that date have declined year by year through the fiscal year ending June 30, 1949. An upward trend was noted in the fiscal year 1950 but the significance of this development is not clear." When you look at the chart of supporting evidence, you see 3,411 cases in 1945 versus 1,999 in 1950, so overall it's a significant decrease during the years in question.
Harold R. Muntz, Chief Probation Officer, Hamilton County, Ohio indicated an increase in delinquency complaints for 1948 and 1949 (the 1950 data were incomplete). From 1945 to 1949, the number of delinquency complaints went from 3,491 to 3,679, which is an increase. Muntz attempts to provide per capita data, but uses the 1940 census data in all years, making the per capita data rather useless because it doesn't take into account any postwar population increase.
From the commissioner of the North Carolina Board of Public Welfare, "There is no indication that juvenile delinquency has increased during the last 5 years."
Okay, I'm not going to sum up the entire report. That's just the first few responses the Senators list in the report. Suffice it to say that some evidence pointed to an increase in juvenile crime, some pointed to a decrease, and some was inconclusive.
Much of the anti-comics hysteria was driven by emotional reactions to specific events (e.g. man murders his wife after reading Crime Does Not Pay, kid dies after wrapping a towel around his neck and jumps of a building in an attempt to fly like Superman, and so on). Not unlike the later Manson/Columbine episode, people would have emotional reactions to horrible things they read or heard about, and they would want to "do something" to keep the horrible thing from happening again.