The Dow Jones Industrial Average has risen approximately 60% since the day President Trump was elected in November 2016 and more than 380% since the Great Recession low on March 9, 2009. While it’s great news for many people, it does raise questions: With people’s wealth rising, what does the increase do to their estate plans, especially the plans of married couples?

Take, for example, a married couple who came to you anytime between 2010 and the 2016 election. The federal estate tax in 2010 was reinstated after a gradual phaseout, but the exemption rose to $5 million (with inflation adjustments after 2011). Most clients and their estate planning attorneys at the time likely gave little thought to the idea that the Dow would rise by so much so quickly.

Before 2010, advisors tackled estate plans with “two share” or two trust plans that absorbed the smaller exempted amounts into one trust upon the death of the first spouse and saved the rest of the assets for another trust to be used upon the death of the second spouse (attorneys applied these strategies for married couples when there was serious concern the federal estate tax exemption could drop back to $1 million—since nothing is really permanent).

The $5 million federal estate tax exclusion changed that, and estate planning attorneys shifted to “joint” plans for many married couple clients. These plans roll all assets into joint trusts or shares, and do not separate the couple’s assets into separate trusts or separate shares before the death of the first spouse. These are much simpler plans for couples to administer and normally produce better income tax basis results for their heirs. If used properly, these joint estate plans can also produce asset protection benefits for couples residing in so-called “tenancy by entirety” states (where the couples both mutually own undivided property).

Let’s say a married couple in their 60s is at or nearing retirement and has a total net worth (including life insurance and retirement plan and IRA benefits) of up to $4 million. This couple might have been ripe for a joint estate plan after 2010, given the $5 million exemption (and inflation).

But now let’s assume the couple executed a joint estate plan the first week of November 2016. A conservative estimate is that this couple’s net worth has risen by 50%, to $6 million. How is this increase in their net worth relevant to the estate plan now?

Some may argue that, since the federal estate tax exemption has risen to $11.58 million, a joint estate plan is still appropriate. But things change. The $11.58 million exemption is scheduled to drop to approximately $6 million in 2026, and that could drop even farther (and earlier) if Donald Trump is not in the White House next year.

What if one spouse dies today, when the exemption is $11.58 million, but the surviving spouse lives until 2026, when it has shrunk to $6 million? If the surviving spouse’s net worth grows before then, each excess dollar of growth over the $6 million federal estate tax exemption could be taxed at 40% or more. These numbers don’t even factor in the possibility of the surviving spouse dying in a state that imposes its own estate or inheritance tax, at potentially lower exemption amounts.

Others may argue that the so-called “portability election” available under federal law solves all of these problems, because the surviving spouse can add the predeceased spouse’s “unused” federal estate tax exemption onto his or her own $6 million federal estate tax exemption, thereby eliminating the concerns of tax law changes. But even if we ignore the fact that the federal portability election is unlikely to be available for estate and inheritance taxes at the state level, and is definitely not available for federal generation-skipping transfer taxes (a topic beyond the scope of this article), is this generalization about the federal portability election true?

In fact, the portability amount will not be available to the surviving spouse if he or she remarries and the new spouse dies first. Although the surviving spouse may be entitled to a portability election applicable to the new spouse, there is no guarantee a portability amount will even be available at the new spouse’s death. The new spouse’s estate may be large, or the federal estate tax exemption at the time of his or her death may be smaller. And we’re still putting aside estate and inheritance taxes at the state level as well as federal generation-skipping transfer tax issues. These might have been blunted or eliminated if a “two-trust” or “two-share” estate plan had been used at the time the first spouse died.

What this means is that, after the 60% run-up in the Dow, some married couples might need to rethink their estate plans if they switched to joint wills or trusts in the last 10 years. This is especially true if one spouse is likely to remarry upon the death of the other. Otherwise, these couples risk surprising federal or state estate taxes, inheritance taxes or generation-skipping transfer taxes when the surviving spouse passes away.

James G. Blase, CPA, JD, LLM, is founder of Blase & Associates LLC, a St. Louis-area law firm practicing primarily in estate planning, tax, elder care, asset protection, and probate and trust administration. Mr. Blase is also an adjunct professor at the St. Louis University School of Law and in the Villanova University Charles Widger School of Law Graduate Tax Program.