based on survey data from the Pew Research Center.

Researchers asked U.S. adults in early 2020

which issues they think should be top priorities

for the President and Congress.

The top two issues were the economy and the environment.

Now, as we compare that to other years,

you can see that these two policy issues

haven't always been top of mind,

although the economy has ranked 1st since 2002.

Until recently, jobs were second.

The environment was last place for several years,

and climate change didn't even make the list until 2015.

So what's going on here?

Questions like these help political scientists

measure the policy mood of the public,

people's preferences toward policy choices.

As you can see, policy mood changes over time,

in response to problems and issues that arise.

For example, in 2009, as a response to the economic crash,

surveyed adults responded that jobs

should be a top priority, but in 2020,

after a period of economic recovery and low unemployment,

jobs had fallen as a main concern and new issues

had taken its place.

Climate change has become a major concern

for many people, which wasn't even a term

that people knew a few decades ago.

Conversely, a poll like this taken in 1980,

might have shown containing Communism as a main concern,

but since the fall of the Soviet Union,

that has dropped off the list.

These measures of policy mood help politicians

and political parties craft their policy agendas,

in order to attract voters and serve their constituents.

But if so many people think that the economy

should be a major priority, why don't voters

all just agree on a course of action?

Here's where ideological differences come into play.

Political scientists sometimes divide policy issues

into position issues and valence issues.

Position issues are issues that divide voters,

like abortion or gun control, where there isn't much room

for overlapping opinions.

Valence issues are issues that most voters will agree with,

like our communities should be free of crime

or we should care for the elderly.

These are high level values that cut across partisan lines,

but the parties might differ

on how to achieve those outcomes.

For example, although both Democrats and Republicans

might want to reduce drug use, Republicans might argue

that tougher drug laws are most likely to achieve that goal,

while Democrats might argue that prevention

and education programs would be more effective.

So policy mood tells us what the public thinks

is most important at any given time,

but differing ideological beliefs about how best

to achieve those priorities lead to different approaches

on the left and the right.