Demand keeps outpacing supply in a Boston real estate market that's been showing gains on an annual basis for months.

According to the Greater Boston Association of Realtors (GBAR), this June low mortgage rates, rising home values and a healthy job market kept demand for detached single-family homes on the up-and-up. Sales of those units have been improving on an annual basis for 13 straight months, up to 1,916 this year from 1,870 units sold last year. The previous monthly high was June 2004's 1,888 sales.

Meanwhile, condo sales remained essentially flat, 1,388 to last year's 1,389. That's still the third highest sales total for June in greater Boston; the highest was 2005's 1,546.

The June single-family median price was 4.5% higher than it was last June, $585,000 to 2015's $560,000; this was the 21st consecutive month that it's risen on an annual basis. Condo prices were also up, $505,000 to last year's $460,000, an increase of 9.8%.

Inventory, on the other hand, continues to drop as the housing stock stays flat and the buyers keep coming anyway. Single-family home inventory dropped 18.5%, from 3,698 in June 2015 to 3,015 last month. Condos went from 1,933 to 1,457, a 24.6% fall.