Yesterday I argued that if you want to discuss what changes to household debt might mean, you need a decent framework for assessing the fluidity of the microstructure of debt. To illustrate I set out two hypothetical countries with identically modest aggregate household debt loads – but with different sensitivities to changes in interest rates, and differing levels of financial stability. I called them Debtzania (where debt is concentrated and debt-to-income ratios for debtor was high) and Feudaland (where debt is thinly spread and a few households are creditors).
Which of these economies does the UK most resemble?
Using the NMG/ Bank of England survey data we can examine where it is in the income distribution that UK household debt falls.
Table 2 shows that most debt is owed by those in the top three deciles of the income distribution, and on sums below £175k. The mortgage-dominated nature of this debt and the untroubling LTVs with which it is associated may explain it to some as both rational and desired.
Table 2: Where household debt sits, by pre-tax income decile and total debt cohort
We can perform the same analysis for deposit balances held among our sample (knowing that at the macro level, total monetary assets and total monetary liabilities in the household sector are roughly the same), the output of which is shown in Table 3. It is perhaps not surprising that most of the money is owned by members of the upper half of the income distribution.
Table 3: Where household deposits sit, by pre-tax income decile and total deposit cohort
We could treat each income decile as a separate sector and look at the transfer of net monetary claims between them (in the form of savings and borrowings). This is shown in Table 4, and the data suggests that the flow of savings is on a net basis from lower income cohorts to upper income cohorts, typically to deliver mid-sized mortgages (we could, of course, reverse the causality in this description). This concentration of debtors might sound a bit more Debtzanian than Feudalish.
Table 4: UK households by pre-tax income decile and total debt cohort, estimated net saving/ borrowing flow
But debt sustainability is only really an issue for those in debt, and will correspond to their ability to service debt. And so in Table 5 we examine how debt-to-income ratios vary across the our matrix of UK household debt and income distribution. After all, small cohorts of high debt-to-income ratios was the thing identified as problematic when looking at otherwise untroubling Debtzanian aggregate debt statistics. Here we can see that debt-to-income ratios look pretty high for almost all debtors, but least troubling for highest income households where most nominal debt resides.
Table 5: UK household debt-to-income ratios, by pre-tax income decile and total debt cohort
And so the problems for policymakers seeking some rules of thumb to estimate sustainable or unsustainable levels of household debt appear twofold.
First, there is a data issue. Our sample size of around 6,000 households is small (as evidenced by @jmackin2’s outrage yesterday), even before we start to exclude households that refuse to give data in which we have interest. For the purpose of this blog I have used a snapshot, but I think that we need to compare datasets on a longitudinal basis. When the numbers on the matrix change, we need to understand whether this the result of movement on the income dimension or debt dimension.
Second, we have a question over the appropriate unit of analysis. In discussing Feudaland and Debtzania we argue against this being the overall economy, but as suggested by a comparison between the matrices of debt and income distribution on the one hand, and deposits and income distribution on the other, splitting the population into income deciles takes us not much closer to the issue at hand. There are meaningful flows between debtors and creditors within members of any given income decile. The appropriate unit of analysis is perhaps the household. But that statement seems a bit nuts.
The chart below looks at individual households in the NMG survey, rather than treating them as aggregated cohorts. It’s messy, but maybe messy is what works.
Putting aside human concerns for families struggling with the very real problems attached to sever indebtedness, why should policymakers care?
FPC members care because widespread unsustainable household debt can lead to problems for financial stability. But, through this lens, problems in debt service among low income households with small but unsustainable debt balances are just not worthy of deep interest: they are insufficiently likely to cause systemic financial problems.
MPC members care because changes in appetite for debt might tell them something about the location of the neutral real interest rate. Through this lens it might seem that it doesn’t matter what individual households are doing, but does matter what they collectively do. And I guess that if this is true, changes in the optimal level of debt which can only be inferred from an examination of its microstructure will be an important in any decision as to the wisdom of ‘leaning against the wind’. And they will care because cashflow impacts for indebted households following changes in interest rates are part of the transmission mechanism.
What to do?
Despite data shortcomings, there are some suggestions that we can draw out. First, in considering changes to household debt, policymakers should do well to treat aggregate debt statistics with caution. Having an idea as to whether they are dealing with Feudaland or Debtzania, and the degree to which there is stability in the microstructure of the debt distribution seems important. Second, examining the entire distribution of nominal debt-weighted debt-to-income ratios (and changes thereof) appears to be a step towards more capturing more meaningful household debt characteristics, changes in household behaviour and systemic debt problems.