Writing in wet cement is a harmless rite of passage that lets kids feel more strongly bonded to their community and to one another, while also filling their need for risk-taking in a way that stops short of setting a dumpster on fire.
I still remember the day when they finally began to re-do parts of the sidewalk in front of my house when I was about 10 years old (around 1990). At last the opportunity had come! I think I just inscribed my first name and last initial, nothing more pretentious than that. Many foolish commentators, both those in favor of and against the practice, interpret scrawling your name in the cement as an act of ego-inflation, maybe even a grasp at immortality. But no one who's actually done it would think that.
For one thing, few leave their full names. During my daily walks over the past couple weeks, I've looked for any carvings I could easily spot, and only one had someone's full name -- although not the writer's name, but that of his crush or girlfriend ("I LOVE KELLY GREEN!"). Most people don't have very distinctive first names, even less so if they only leave their initials, which could hardly be more anonymous. So clearly this is not an attempt to make posterity aware of your specialness.
The practice instead resembles leaving your name in a guestbook at a social event, or signing someone's yearbook. We wrote our names just to show that we were part of the broader group of people who would read them. Our exact identities were not important because the average pedestrian would not know us personally. All that counted was the signal that there were a good number of people in their neighborhood who felt loyal and excited enough about living there to sign its guestbook.
The second-most common form -- "boy + girl" -- serves much the same function. It's a pre-adult version of a wedding announcement, for those not advanced enough to merit a spot in the newspaper. It reassures the community members that boys and girls are getting along well with each other, whoever they are, and that their relationship is not shallow -- you have to be pretty committed to carve "ZACK + KELLY" into cement.
However, as social bonds began weakening in the early 1990s, young people have found less and less meaning in leaving their mark on public spaces. If they do not venture around the neighborhood, it is not really theirs. If they are mostly locked inside with no social life, there is no larger group to pledge loyalty to in such a risky way. And if they don't start going out on dates and making out until college, there is no declaration of love to be made.
Not surprisingly, none of the dozens of carvings that I saw on my walks were from the 2000s, only one or two were from the later half of the 1990s, although there were a good number from the early '90s, and a handful from '93 and '94. Most of them, and particularly the more group-oriented ones (where several friends or couples joined in at the same time), are from the '80s or the late '70s.
How can you tell? Often a year is explicitly written, sometimes down to the day -- "Oct 11 '79 Gus." Even without a year, they can be roughly dated by the names shown -- "Tommy [heart] Linda" and "Tim loves Dawn" cannot be from the mid-'90s or later because when was the last time there were teenagers named Tommy, Linda, Tim, and Dawn? They're all ones that were popular among "late" Boomers (born from '58 to '64) or Generation X (born from '65 to '78). In contrast, there are none with Millennial names (born from '86 on). Aside from their weaker relationship bonds, they've also got the problem that it would sound too funny to take seriously -- "Tanner + Morganella" sounds more like the name of a queer bookstore / sex shop than of two wholesome young lovers.
As with crime in general, the ramping up of punishment lagged several years after the crime rate itself had plateaued or started to decline. I searched Lexis-Nexis for any articles mentioning "wet cement" from the 1980s and earlier, and found none that mentioned police action against youngsters. For the 1990s and later, I searched for "wet cement" and "police." I'll put the article excerpts in the comments for the curious -- all meant for the "funny if it weren't pathetic" file. Briefly, the earliest item is a police blotter notice from late November, 1995, followed by full articles about kids in late elementary school or middle school getting arrested and brought to court in '97, '99, 2001, '06, '06 again, and '11.
It's another example of greater authoritarianism from rulers, and greater acceptance of it among the ruled, which takes hold only during falling-crime times. In rising-crime times, the rulers have more pressing matters to deal with, and citizens choose greater independence from the government, having witnessed its inability to socially engineer a crime-free utopia.
Shifts in national public policy are simply too slow, too impotent, and too clueless of the facts on the ground to have a drastic impact on criminal behavior. (I might provide time-series graphs of incarceration rates and homicide rates later to illustrate this.) This is another case, where only after the practice was already dying out did the police bother to drag 11 year-olds in front of a judge for writing their names in wet cement.
We find a parallel in carving your name into tree trunks, which was just another form of public-space carvings. You haven't seen those in forever, and unlike with wet cement carvings, there have not even been any police crackdowns. That's because trees carvings are less visible, whereas sidewalk carvings are not hard to see and could more easily frighten some spazz who cares more about squeezing every cent out of his property value than he does about a spirit of neighborhood togetherness and making sure the young feel included. As with sidewalk carvings, here punishment was not necessary because the desire to do it in the first place had begun to fade out. Such punishment as there was served only as a delayed symbolic message that the times had changed.