The Problem of Missing Non-Voters

In short

Missing non-voters: Non-voters are less likely than voters to answer surveys.

A Pollster Calls

People who do not vote are less likely to participate in surveys than voters.

Voters and Population Weights

The problem of missing non-voters arises when we seek the views of voters, but demographic weights for the country’s adult population are applied.

Our hypothetical population has been scaled down to 1,600 people.
The Blue lead here is eight points, as that party has 540 out of 1,000 voters (54% — 46% = 8%).
The Red lead is five points, as that party has 525 out of 1,000 voters (52.5% — 47.5% = 5%).

Responding to Non-Response Bias

Responding to the missing non-voters problem, two methods were used in 2017 General Election polling.

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