Thank you for taking a look.  I'm using the following URL:

    http://api.bitcoincharts.com/v1/markets.json

Firebug shows me the following response header with no gzip:

    Connection   keep-alive
    Content-Length   31457
    Content-Type   application/json
    Date   Mon, 02 Sep 2013 21:47:42 GMT
    Server   nginx/1.5.

If I compare the Content-Length to the size of the actual content in the browser I also get 31457 bytes, also indicating it wasn't compressed.

But if I use a URL that returns CSV for Historic Trade Data:

    http://api.bitcoincharts.com/v1/trades.csv?symbol=mtgoxUSD

The response header is:

    Connection   keep-alive
    Content-Encoding   gzip
    Content-Length   164644
    Content-Type   text/html; charset=utf-8
    Date   Mon, 02 Sep 2013 21:52:48 GMT
    Server   nginx/1.5.0
    Vary   Accept-Encoding

This shows the response is compressed and the size of the actual data in the browser is 861429, also indicating it was compressed down to 164644 byes.

I've also tried the following URL:

   http://api.bitcoincharts.com/v1/weighted_prices.json

This doesn't appear to be using compression either so I'm assuming the server isn't configured to compress content type 'application/json'.

J