Attributes per user
<%= column_chart User.joins(:attribute_fields).group(:user_id).count().group_by { |n| n.last }.each_with_object({}) { |(content_count, ids), h| h[content_count] = ids.count } %>
<%# TODO: attributes per each content type %>
Attribute privacy
<%= pie_chart AttributeField.where.not(privacy: "").group(:privacy).count() %>