We have been privileged to experience breathtaking progress in public opinion on same sex marriage in recent years. The latest polls hover around 55%, up nine points since 2011. However, the diminishing number of opponents also means that there will no longer be room for acceleration, quite the opposite. Barring some jarring events (oops that rhymes), we should expect to see growth to taper off just as slowly as it started. Just how much?
In the year 2026, support for marriage equality will reach 75%. Find out why below
Having passed the 50% inflection point a few years ago, the data on the slowdown is just starting to come in. A rich source of polling data on this issue may be found here http://pollingreport.com/civil.htm. See table below.
Of course, with data comes the ability to model graphs and forecast the future. Because the parameters of percentage are certain (0-100), it is fairly easy to construct a reliable logistic function without viewing very far into the future. The higher quality the data the better the graph will be, especially the end points on regression lines. The earliest I could possibly find a poll was in September 1985 through a secondary source.
Without going into higher math (Taylor series, sums, calculus, etc.), a very basic discussion on how logistic functions are extrapolated from data can be found at this link: http://www.cs.xu.edu/math/math120/01f/logistic.pdf
We will pick two points the get our equation for the graph, the first, and the half way point. I won't bore you guys with the details on how I did it. Follow the link. Through some mathematical trickery we arrive at the equation and graph with the points plotted alongside it.
We can use this equation to predict the future.
Suppose we we want to know when will support reach 75%. Look at the graph, or for an exact figure just solve the equation for 75.
75 = 100/1+8.1e^-0.0774(x-1985)
100/75 = 1+8.1e^-0.0774(x-1985)
0.3333 = 8.1e^-0.0774(x-1985)
0.04115 = e^-0.0774(x-1985)
ln0.04115 = lne^-0.0774(x-1985)
-3.19 = -0.0774(x-1985)
41.22 = x - 1985
2026 = x
So in the year 2026, support for marriage equality will reach 75%
Year Support (average) 1985 11 1988 12 1994 21 1996 26.8 1998 29.0 1999 34.5 2000 34.0 2001 35.0 2003 34.1 2004 32.6 2005 36.7 2006 37.3 2007 40.7 2008 41.6 2009 41.4 2010 44.3 2011 49.0 2012 49.8 2013 53.4 2014 55.5
Raw data available upon request.