The numbers don't lie...
True. Also true: you don't understand what they're saying.
Their is a linear line in the graph between Leap seconds added and the number of years that have passed

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The data
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OK. So? A straight line means the earth's rate of rotation isn't changing. The line would be curved upward if the earth's rotation were slowing, but over the 44.5 years between the first and last data points, the rate hasn't changed enough to see that amongst the noise. This graph suggests that the definition of the second is a little too short.
Here's a better plot, without the extraneous data points.

Plotted data from here:
https://www.timeanddate.com/time/leap-seconds-future.htmlThis plot also shows the formula for the regression line. Since X = 0 is the beginning of Dec 31, 1899, the intercept is kinda meaningless, but the slope is what we're interested in. Excel reckons time in days, so 0.0016x means the earth's rotation averages 1.6 millisecond longer than the nominal civil day (neglecting leap seconds), accumulating to a full second of error every 625 days, on average (1/0.0016 = 625).
There's no direct evidence in these plots that the earth's rotation is slowing. If anything, it vaguely suggests that it's speeding up, but there too much noise in the data to draw definitive conclusions from this data alone.