How educated will the 2020 electorate be, relative to the general population?

[Senator Incitatus]

For context, here are some historical numbers. I used data from the U.S. Census to calculate both columns.

YEAR	% POP	% VOTER	DIFF
1980	17.25	20.65	3.40
1984	19.30	22.22	2.92
1988	20.50	25.51	5.01
1992	21.45	26.58	5.13
1996	23.70	29.38	5.68
2000	25.70	31.16	5.46
2004	27.75	32.42	4.48
2008	29.45	31.53	2.08
2012	31.00	36.60	5.60
2016	33.45	39.60	6.15

[Storr]

For context, here are some historical numbers. I used data from the U.S. Census to calculate both columns.

YEAR	% POP	% VOTER	DIFF
1980	17.25	20.65	3.40
1984	19.30	22.22	2.92
1988	20.50	25.51	5.01
1992	21.45	26.58	5.13
1996	23.70	29.38	5.68
2000	25.70	31.16	5.46
2004	27.75	32.42	4.48
2008	29.45	31.53	2.08
2012	31.00	36.60	5.60
2016	33.45	39.60	6.15

That large jump in the difference from 1984 and 1988 is interesting. Any guesses as to what caused that?
The Obama factor in 2008 of energizing African-Americans in particular, but all other voting demographics as well, is clear.

[forza nocta]

What was the cause of that swing between 2004 and 2008 and then in back in the other direction in 2012?

[Senator Incitatus]

That large jump in the difference from 1984 and 1988 is interesting. Any guesses as to what caused that?

Beats me. Could just be that both candidates were seen as elitist. In 1980 and 1984 the candidates were significantly more "populist" and centered their campaign on less educated voters. In 1988 the campaign was centered on the suburbs.

What was the cause of that swing between 2004 and 2008 and then in back in the other direction in 2012?

Likely black turnout, but also less-educated whites and minorities.