Only the current version so far — new entries appear as the app ships updates.
ECM J/S ratio (SOJ) is a tools app by Randle Christian Sink with 1,000+ downloads (about 3K estimated). Released Mar 11, 2015. Install growth, rank history, SDKs and ad networks.
From the store listing: “Electronic Counter Measures (ECM) calculates J/S ration for SOJ situation...”