Answer: interest rates dropped, which led to more home starts.
In the first graph, we can see a sharp rise in interest rates around the year 1983. At the same time, we can see an increase in home starts in the second graph.
The 1980s saw a huge increase in interests rates, sometimes as high as 17-18%. This made it difficult for families to afford a house (by comparison, interest rates nowadays are around 3-5%). The high interest rates were an attempt to control the problem of inflation.
