可能需要提供更多的上下文信息才能更好的理解把。
最好还把论文的题目和摘要也贴出来。

缺乏上下文，语义看起来不完整。字面意思的理解上好像是有点冲突？
我简单试试字面的意思，楼主结合自己的理解把正确的含义梳理出来吧。
分布的均值趋于增长，因为预测人不愿意把高于均值的预测聚集在一起？
读起来好像是怪怪的

差不多是这个意思

分配的均值趋于增长，因为人们很少愿意去约束那些高于均值的预测。

The reduction in the dispersion of the forecast
distribution occurs because individual forecasters
"revise" their published estimates toward those of
their colleagues. The mean of the distribution
tends to increase because forecasters have less
incentive to "herd" their above-average forecasts.
In particular, ceteris paribus, more optimistic forecasts
are usually better for the investment business
than less optimistic forecasts.