Unlike bar charts and histograms, you do not need to include a zero baseline for a line chart. The main goal of a line chart is to emphasize changes in value, rather than the magnitude of the values themselves. When a zero line is not meaningful or useful, it’s fine to zoom the vertical axis into a more informative range. However, when a line chart is used to display frequency distributions, then it will require a zero-value baseline to anchor the line chart’s heights.