June's games and their associated data are complete: the early swoon abated in the second half of the month, keeping it essentially on track with the R/G, HR/G and BB/G produced in May. The comparison of June 2018 with June 2017 still remains stark, however, as our differential percentage chart indicates.
Another way to track this data is to pick a "base month" and measure the monthly deviations from it that occur over time. There are actually two ways to do this--one where you track the changes month-by-month, using the prior month as the basis for the calculation, and other where you measure every month against the "base month" and get a cumulative rate of change.
Both are of sufficient interest to display here. First, the month-by-month changes [at right]. The "base month" we're using here in September 2017, the "cool down" month in last year's long homer siege (4.58 R/G, 1.19 HR/G, 3.25 BB/G). We can then see that April 2018 hit less HRs but drew more walks: the net result was a slight downturn in run scoring. May gained in HR/G over April, but pitchers were much stingier in terms of walks, which caused another downturn in R/G. And our comments comparing May 2018 to its successor month can now be seen in percentage terms, where runs went up slightly despite small declines in HR/G and BB/G.
But in May we see the "cumulative" effect kicking in. We can see that relative to September 2017, May 2018 shows a larger cumulative drop in R/G, brought on by the flip-flops in HR/G and BB/G that show a cumulative decline in each of these measures. The June data shows how this data starts to converge, as the combined cumulative downturn in HR/G and BB/G is now about 80% of the decline in R/G.
What can we expect in July? There's often a decline in HR/G and R/G from the peaks achieved in the previous month; last year was no exception. It's possible that the protracted batting average swoon that occurred in the first half of June might have righted itself, however, and we may see some modest gains in July. Stay tuned...