Normalized Stacked Bar Chart
This is an example of a normalized stacked bar chart using data which contains crop yields over different regions and different years in the 1930s.
import altair as alt
from vega_datasets import data
source = data.barley()
alt.Chart(source).mark_bar().encode(
x=alt.X('sum(yield)', stack="normalize"),
y='variety',
color='site'
)