Why has the Appen (ASX:APX) share price leapt 18% in a week?

The S&P/ASX 200 Index (ASX: XJO) has enjoyed a bumper session over the past week or so. Since market close last Wednesday, the ASX 200 has managed to add a very healthy 2.22%. Bt one ASX 200 share has run laps around even that esteemed performance. That…