Mayor Michael Bloomberg of New York City warned Friday that if the U.S. economy did not soon create a sufficient number of jobs for its people, the nation could witness the kinds of street rioting and civil disturbances recently seen in places like Cairo, Egypt and Madrid, Spain.

Bloomberg said on his weekly radio program: We have a lot of kids graduating college, can't find jobs. That's what happened in Cairo. That's what happened in Madrid. You don't want those kinds of riots here.

With the national unemployment level staying stubbornly high around the 9 percent level, Bloomberg is right to call attention to the problems of chronic unemployment and companies reluctant to start spending on hiring.

But his warnings about street violence seems rather far-fetched and alarmist.

The fact of the matter is that violent crime in the United States has been falling across the board for at least the past five or six years.

While no one is complaining about this development, it is baffling to experts, given that the nation's population has been steadily climbing, drug abuse remains widespread and the economy has been battered.

According to the Federal Bureau of Investigation (FBI), violent crime (which includes rape, murder, armed robbery, aggravated assault, etc.) dropped by 5.5 percent last year, while property crimes (like burglary, auto theft, etc.) fell by 2.8 percent. The declines were particularly pronounced in the South, Midwest and Far West.

Consider the sprawling metropolis Los Angeles, which at one time was beset by gang warfare, drug trafficking and murder. Violent crime plunged by 8 percent in the first half of 2011 -- in accordance with a decade-long decline.

Los Angeles is also now ensnared in a huge fiscal crisis that has hammered the entire state of California.

While the murder rate in New York City rose a bit last year, the 600 or so murders the Big Apple has been recording the last nine years is dramatically lower than the 2000-plus homicides reported in 1990.

Criminal behavior is extremely complex and there is always a confluence of factors that determine its incidence.

International Business Times recently spoke with Susan Koski, professor of criminology and criminal justice at Central Connecticut State University in New Britain to explore this unusual social trend. (The interview was conducted prior to Bloomberg's comments).

IBTIMES: Violent crime in the U.S. has been falling for the past several years, despite a growing population and (since 2007) a worsening economy. Does this surprise you, or are there some legitimate factors behind this phenomenon?
KOSKI: Yes, it does surprise me to some degree, given that stress and joblessness often contribute to criminal behavior.
But there are many types of crime and although violent crime (typically murder/non-negligent manslaughter, rape, robbery, and aggravated assault) may appear to be declining, other types of crime that are more closely related to the worsening economy such as property crimes may be on the rise.
It is also important to keep in mind that data from the FBI's Uniform Crime Reports (UCR), although supposedly uniform, may not actually be so. Each police department classifies crimes differently -- and therefore they may
categorize their crimes differently when reporting to the FBI.

IBTIMES: Could demographics be playing a role? That is, even if the overall population is climbing, people are also aging rapidly, thereby reducing the percentage of the population that is youthful (who tend to commit most violent crimes)?
KOSKI: I think this has more to do with prevention. Police are perhaps more successful today at deterring young people (through targeted programming and governmental funding) from violence and are, therefore, driving violent
crime rates down.
On another note, although age and employment rates are often linked to criminal behavior, the research consistently show that this is not a factor in juvenile arrest rates (primarily because they are not in the job market).

IBTIMES: Between, say, 2005-2010, did we see more police getting hired and more aggressive tactics by cops?
KOSKI: Actually, many police departments have been unable to hire due to hiring freezes or other funding issues, but technology has also improved and advances in technology/software has aided departments in their deficits.

IBTIMES: How have technological developments like DNA testing and the proliferation of surveillance cameras helped to reduce crime?
KOSKI: Although these are often controversial elements in preventing crime, they do have important qualities. DNA testing in particular in association with the Innocence Project has helped to free many innocent people.
Cameras, like other prevention techniques are helpful, but with the advent of any new technology, the criminal will adjust his/her tactics as well.

IBTIMES: Now that state and municipal governments are cutting spending and enacting layoffs (including police), are we now liable to see a uptick in crime?
KOSKI: Perhaps, but as I already mentioned, there have been advances in technology that are adjusting for the gap in hiring.
It is also important to keep in mind that with a decrease in law enforcement officers, there may also be a decrease in crimes being reported.
The UCR data compiled by the FBI relies on information provided to them by the police departments - but, if the departments are under-staffed, there may be less attention to this task. This often leads to departments not contributing at all to the report -- typically already-underfunded departments and often the ones with the most crime to report.
Moreover, in the last few years, police department budgets have shrunk, resulting in a return to general law enforcement duties and a decrease in specialized crime units (gangs, vice, cyber, etc.). Thus, initial arrest rates of crimes, which require specialized or long-term investigations, decline.
Also, the investigations of petty crimes decreased due to manpower being diverted to focus on major crimes/first responders.
Policy decisions to not prosecute simple drug offenses also have had a significant impact.

IBTIMES: What about incarceration? Are more criminals being sent to prison and getting longer sentences? Could this be a factor in reduced crime?
KOSKI: There has been a steady increase in incarceration for more than three decades. Longer sentences have contributed greatly to the nation's prison overcrowding, but in turn this has contributed to mass release in recent years.

In 2009, 1 in every 47 U.S. adults was on some type of community supervision (probation or parole). These decreases are consistent with legislation in certain areas. Many offenders, especially high-risk offenders under intensive supervision, produced an increase in arrest rates (both technical violations and criminal offenses).

Keep in mind; some states have greater population of prisoners/probationers, so they drive the nation's numbers.

For example, consider California's third strike laws -- in 1994, this law went into effect following the rape and murder of Polly Klaas.
This led to longer prison sentences - which, in turn, are believed to have led to an increase in the prison population and a decrease in crime rates by repeat offenders. California has also drastically reduced its parole population.
However, recent legislation has increased local community supervision options in order to meet the Supreme Court's ruling that mandates reductions in prison overcrowding.
With regard to the courts, every state differs here as well as every crime.
For example, there have been stiffer penalties for drunk driving in recent years, less stiff for marijuana incidents; more stiff for certain sex offenses, etc. This is a product of various policy initiatives and media attention.

IBTIMES: How about the internet and mobile phones? Could the huge popularity of such devices among people (regardless of income or race) also be lowering violent crime rates?
KOSKI: To my knowledge, there isn't extensive literature which discusses the correlation of phone use and violent crime. In fact, the Internet is often used as a device to commit crime, sometimes for the organization of violent
crime, but many of those crimes are under-reported or unknown at this time.
In terms of accessibility to phones and whether criminals are less likely to commit for fear of being caught, premeditated violent crimes are rarer and often such crimes happen in a fit of rage or considered crimes of passion- thereby, with culprits not considering the immediate consequences.

IBTIMES: Is it true that violent crime fell during the Great Depression of the 1930s? If so, what does this say about criminal behavior and economic hardship?
KOSKI: Actually, violent crime increased between 1920-1940 as employment levels increased, which is a different trend than what is typically expected and the reason for this is unknown.
It is important to keep in mind that race plays a critical role. Different races respond differently to economic changes leading to variation in the reaction to a changing social structure. Blacks, Latinos, and Whites respond differently and at that time were impacted differently by economic shifts.
Violent crime appeared to be on the decline after this time and began to increase again around the 1960s and 1970s and again in the 1990s with the crack epidemic.

IBTIMES: How does the drug culture fit into this? We may start to see more states legalize marijuana - will this reduce drug-related offenses?
KOSKI: Many states are beginning to decriminalize marijuana, which is different from legalizing it. Most are imposing less severe sanctions on minimal amounts only. It is hard to say, since each state has differing legislation here. Research appears to conclude that this will aid in reducing the prison population and overall recidivism rates.
There is also some evidence that a shift from illicit drug consumption to prescription drug abuse has not been adequately addressed by law enforcement. A shift has not occurred to meet the changing face of the criminal acts or the population of offenders.

IBTIMES: Also, the crack epidemic appears to be over. Surely, this has lowered murders and robberies?
KOSKI: Violent crime is often linked to drug use and mental illness, so it is likely that this will have some impact, although it appears to have more to do with urban socioeconomic shifts in more recent years.
Reports of drug use while committing a criminal act remain high and although there are more substance abuse treatment programs today than previously, they are often the first to be eliminated in a struggling economy.
It appears that this group [drug users] is the highest risk for offending and reoffending given the many factors contributing to their substance abuse in the first place.
Also keep in mind that new weapons and technology leads to new crimes every day. It may not necessarily be violent crime, but criminals will always find a means to their end.

IBTIMES: Did violent crime peak in the early 1990s? And did that coincide with the crack cocaine trade?
KOSKI: Yes, homicide rates for certain groups (Blacks and Latinos) more than doubled between the mid 1980s and mid 1990s. In distinct areas nearly 60 percent of drug-related homicides were reportedly tied to crack.
The reason for such a spike in crime (not just violent, but property as well) was primarily due to users wanting money for the drug, but also for traffickers protecting their goods.
Other issues arose as well as many mothers gave birth to addicted babies (ending up in foster care). In the mid 1980s there were also substantial legislative efforts (Anti-drug Abuse Acts), which targeted the effects of the crack craze and thereby led to prison overcrowding issues and unjust sentencing.

IBTIMES: Do you think crime will continue to decline in the U.S.?
KOSKI: That's a tough question. I think it's dependent on many factors. If we don't cut the appropriate programs that are meant to help the offenders overcome their difficulties, yes it can possibly continue along this trajectory.
The current austerity budgets of local and national government agencies suggest we will not be investing in evidence-based programs that have rehabilitative or preventative missions.
In addition, the manner in which we treat prisoners today, with little dignity, will make it difficult for them to be rehabilitated. Although there are some that may never be able to make good, ethical decisions, I do believe that most have made poor decisions, but are generally decent human beings. Drugs, alcohol, abuse, poverty, and greed are factors that significantly contribute to whether one enters into criminal activity and or desists from it. How we treat offenders after their offense impacts the next journey on their path and whether they are able to overcome their challenges.
This is especially important considering most will be released into the community at some point.