Trades aggregated by the sector of the stock traded.

Each trade is attributed to the market sector of the stock involved. So Health here means “trades in health-care stocks”, whoever made them — not trades by members of committees that legislate health policy. Assets with no sector on file (bonds, options, funds, delisted or non-US listings) are left out of this view rather than bucketed somewhere they do not belong. See the methodology page for the full caveat.