Harvard researchers David Yanagizawa-Drott and Andreas Madestam suggest that the correlation is a function of the way conservatives have linked their values to expressive displays of patriotism.
"The political right has been more successful in appropriating American patriotism and its symbols during the 20th century. Survey evidence also confirms that Republicans consider themselves more patriotic than Democrats. According to this interpretation, there is a political congruence between the patriotism promoted on Fourth of July and the values associated with the Republican party. Fourth of July celebrations in Republican dominated counties may thus be more politically biased events that socialize children into Republicans," they write.
According to their research, attending one rain-free July 4 celebration before the age of 18 increases the likelihood that children will identify as Republican by two percent and increases the likelihood that they will vote for a Republican candidate by the time they turn 40 by four percent. It also increases the likelihood that young attendees will vote in elections by 0.9 percent and boosts the chances that they'll make political campaign contributions by three percent, the study claims.
While the GOP may be taking this is as an increased incentive to encourage the younger generation to get out and enjoy some Independence Day festivities this year, Democrats will have to come up with another reason. The study finds no evidence that attending July 4 celebrations results in an increased likelihood of identifying as a Democrat.