Edward Tufte's data-ink ratio (The Visual Display of Quantitative Information, 1983) measures how much of a graphic's printed/rendered ink actually encodes data, versus decoration:
Data-Ink Ratio = Data-Ink / Total-Ink
= Data-Ink / (Data-Ink + Chartjunk-Ink)
Here Data-Ink is the true silhouette area of the N bars: Σ(barWidth × heighti) — the only geometry that actually carries information about the values. Every toggle above adds a real 3D object whose own footprint area is summed into Chartjunk-Ink:
- Drop shadow — an offset duplicate slab per bar, area ≈ 0.18 × (barWidth × height)
- Bevel — a fake-depth highlight strip per bar, area ≈ 0.15 × height
- Gradient panel — one large plane behind the whole chart, area = chartWidth × chartHeight
- Gridlines — 5 lines spanning the chart width, area = 5 × chartWidth × 0.03
- Border frame — a perimeter strip around the plot, area ≈ 2 × (chartWidth + chartHeight) × 0.08
A ratio near 1.0 means nearly every rendered pixel serves the data — Tufte's ideal. Toggling every decoration on typically drags a small chart's ratio down to 0.3–0.5, meaning more than half the ink communicates nothing. This is the same trade-off behind "remove chartjunk" advice in real infographic design: gridlines and shadows can aid readability in moderation, but each one has a real, measurable ink cost.