Diagnostic: Profitability trend

The profitability trend is available under the statistics tab in the diagnostic and shows average daily earnings on your account with a profitability range (minimum and maximum peaks of estimated daily earnings; not taking offline periods into account) for the last 14 or 60 days (depending on your account).

You can improve the profitability trend line by optimizing your mining operation and/or careful selection of the coins you are mining. Estimated earnings (profitability) is a product of the hashrate and the coin's estimated reward and to increase it, you would need to increase these two factors.