I have downloaded the following two data sets from Quandl and joined them together to calculate the average deal size.

Venture Capital Investments By Stage - Number of Deals - Quarterly Venture Capital Investments By Stage - Quarterly

And I have applied a time series forecasting algorithm with 'Prophet' R package to understand the overall trend.

One of the interesting insight from the chart above is that, the blue line, which represent the actual investment values in the past have rarely surpassed the orange colored confidence range for all the stages. But one of the times they actually surpassed the upper side of the range was year 2000 when the stock markets went crazy until they bursted miserably. 

Now when we look at the ‘Later Stage’ the blue line is still within the orange colored range, but when we look at ‘Seed’ and ‘Expansion’ stages the recent investment dollars are not just going up but also way above the upper end of the orange color range. So it’s a different pattern from the year 2000 where all the stages went way beyond the general trend, but looks something is boiling up in some segments of the market.