(Added: I have an additional post with more on the effect of RGDP growth on this relationship.)
Thanks, everyone for the comments on this post. I have addressed some issues in the comments there, and added some things in the body of that post.
Some commenters mentioned that using an employment rate instead of total employment might help to get rid of noise due to population shifts, etc. That's a great idea. It's funny how when you're working with data, you don't think of some obvious things.
Many comments have mentioned the effects of the business cycle. Like many of them, I had kind of eyeballed it, and thought there was an unusually high coincidence of recessions following minimum wage hikes.
The comments spurred me to get more specific, and I think, in general, the coincidence isn't as strong as it seems like at first glance. Here are all of the individual graphs from the first post, with the following changes:
1) I changed from teen employment level to teen Employment to Population Ratio (EPR).
2) I added recession bars and also an inverted unemployment rate (for all ages) as signifiers of recession effects.
1956 - a recession coincides with a turndown in EPR, but only for the last few months of the MW period.
1961 - this is coming out of a recession, so there is a downtrend even though the economy should be recovering. There is a recovery in teen EPR after the MW hikes have passed
1967 - no recession during the MW related downturn. Then a brief recovery in teen EPR before a recession that follows
1974 - this MW hike appears to coincide precisely with a recession, so it is difficult to separate the signature of each effect. However, teen EPR begins declining before unemployment. EPR is not usually a leading indicator in recessions.
1990 - the recession begins 4 months after the MW hike. However teen EPR begins declining in the months preceding the MW hike. EPR is not usually a leading indicator in recessions.
1996 - no recession, no MW related decline
2007 - the recession begins 6 months after the MW hike. However, teen EPR begins declining in the months preceding the MW hike. EPR is not usually a leading indicator in recessions.
1 - no MW decline
1 - MW decline not discernible from concurrent recessionary effects, but does have signature of pre-MW downward shift in teen EPR
2 - MW decline precedes recession, with signature of pre-MW downward shift in teen EPR
2 - MW decline with signature pre-MW downward shift in teen EPR, no recessions near MW inception
1 - MW decline, in spite of economy in recovery phase after a recession
PS. The recessions in 1957, 1960, and 1969 are not concurrent with initial MW hikes, but they appear in these graphs. Note that the fall in the teen EPR does not lead the rise in the unemployment rate in these cases.
Here is the graph for the entire period. Full tally of 10 recession and 7 MW episodes:
3 Concurrent recessions & MW, declining trend
7 recessions without MW, declining trend
3 MW without recessions, declining trend
1 MW without recession, climbing trend
All periods with no MW or recession, climbing or accelerating trend