Two neighbor island housing markets moved in opposing directions last month as median home sale prices barely budged on Hawaii island but rose by double digits on Kauai.

The number of sales also diverged, with volume plummeting on Hawaii island and only eking upward on Kauai, according to data from Hawaii Island Realtors and the Kauai Board of Realtors released Sunday by Hawaii Information Service.

The biggest change in the two markets was the number of condominiums sold on Hawaii island. This figure sank 40 percent to 47 sales in July from 78 sales in the same month last year. The median sale price, however, moved only a smidgen to $292,200 from $292,000.

In the Big Island’s single-family home market, the number of sales fell 15 percent to 187 last month from 219 a year earlier. The median price slipped nearly 2 percent to $320,000 from $325,000.

Part of the sluggishness in Hawaii island’s housing market is centered in the Puna area where a lava eruption that began May 3 has destroyed more than 700 homes, buried many residential lots and stopped some people from buying and selling homes in this part of the island that typically has more single-family home sales than any other region on the island.

Puna is almost as big as Oahu; however, the area affected by lava is quite small in Puna. But eruption risk zones are highest throughout the region and have given plenty of people pause about buying a home there.

There were 71 single-family home sales in Puna last month, down 17 percent from 86 sales a year earlier. The median price for those homes was up almost 1 percent at $233,500 from $232,125 in the same period.

Sales of vacant residential land also dropped in Puna. There were 67 such sales in July, down 28 percent from 93 sales a year earlier. The median price, however, surged 61 percent to $25,800 from $16,000.

The median price is a point at which half the sales were at a higher price and half at a lower price. So the size, location, condition and other characteristics of a property can sway the measure, especially when relatively few sales are involved.

On Kauai there were 53 single-family home sales last month, up from 51 a year earlier. The median price rose 11 percent to $625,000 from $565,000.

In Kauai’s condo market, there were 34 sales last month compared with 32 a year earlier, and the median price jumped 33 percent to $480,000 from $360,000. The dramatically higher median condo sale price was partly driven by more higher-end properties being sold. For instance, there were nine sales in the Hanalei region for a median $640,000 last month compared with seven sales for the same median price a year earlier.