An econometric analysis of the equity returns-inflation relationship in South Africa.

Doctoral Degree. Universiy of KwaZulu-Natal, Pietermaritzburg.Previous empirical evidence regarding the nature and magnitude of the relationship between equity returns and inflation has proven to be conflicting and inconsistent. Although several papers have considered this issue, there is still a lack of consensus as to the nature of the relationship between equity returns and inflation. This represents a considerable point of concern as it is this relationship that acts as an indicator of the historical efficacy of equities as an inflationary hedge. While the classical theory dating back to the 1930’s dictates that equities should function as an effective hedge against inflation because they are based on underlying assets with a fixed real value, a substantial number of studies have obtained results that contradict this theory. Many attempts have been made to explain this phenomenon and to resolve the debate since the 1980’s, notably with the application of cointegration theory andmethods (which were developed in the 90’s). Despite advances in econometrics, the issue remains unresolved on an international scale, with conflicting results still occurring in recent studies (Chaves and Silva, 2018; Bhanja and Dar, 2018; Al-Nassar and Bhatti, 2018). The literature that focuses on the South African case is a typical example of the disparity: relatively modern studies using fairly similar statistical approaches find vastly differing results as to the capacity for equities to act as an inflationary hedge, including findings of positive and negative results (Alagidede and Panagiotidis, 2010; Khumalo, 2013), as well as approaches that failed to produce conclusive results (van Rooyen and Jones, 2018). This thesis aims to resolve the issue for the South African case in order to determine whether or not equities have acted as a historically effective inflationary hedge. The South African economy represents a perfect natural experiment for the study due to its high volatility, especially in terms of macroeconomic indicators such as inflation, over the past thirty-five years. The analysis makes use of the Consumer Price Index (CPI) as a proxy for inflation and the Johannesburg Stock Exchange’s All Share Index (ALSI) as a proxy for equity returns over the period 1980 to 2015. The study is undertaken as a collection of publications that each seek to address particular issues, mostly of an econometric nature, that arise when studying the relationship. The first of these papers deals with the disparity in the South African economy regarding the order of integration of the two variables and seeks to provide a comparative analysis with previous studies. Further, the research contained in paper one seeks to identify possible explanations for the conflicting results in previous studies. The study finds that a significant, positive cointegrating relationship between inflation and equity returns exists in South Africa, at least when using conventional cointegration techniques, implying that equities have exhibited the historical capacity to act as an effective historical hedge against inflation, in contrast to the findings of much of the literature. Further, it resolves previous issues with differing findings as to the orders of integration of the variables, which represents a particularly prevalent problem in studies using South African data. While these initial findings would appear to lend support to the conventional theory that equities are able to act as an effective inflationary hedge in South Africa, when examining the issue more deeply it becomes evident that this finding may potentially be impacted by the inherent assumptions of the models employed. Based on the results of previous studies and the results of the first paper, the second paper posits that the equity- inflation relationship is both time and country dependent, potentially contributing to the aforementioned disparities in the existing literature. The implication of potentially flawed model assumptions is that the results of the first paper may be inaccurate (the model risk of a poor model choice giving unreliable results). As a result of this potential limitations bias, the remaining papers of this doctoral dissertation delve into the assumptions behind the classic model, reflecting more deeply on the nature of the data employed and seeking to determine if this relationship holds when various, arguably more realistic, alternate assumptions are considered. The first of these assumptions that is critiqued is that the relationship is time-invariant, such that the equity-inflation relationship does not exhibit variance over time. In an economy such as South Africa, which has shown exceptional macroeconomic volatility, such an assumption may well be inaccurate and is likely to have reduced the integrity of the conventional tests. Relaxing the assumption of time-invariance allows one to consider that the relationship may have experienced shifts over time as a result of exogenous shocks. This idea is tested by investigating the possibility of structural breaks in the individual time series, as well as in the relationship itself. Structural breaks here refer to an unexpected shift in a time series that can lead to forecasting errors, compromising the reliability of the model. Should a model rely on the assumption of time-invariance it is unable to account for the existence of such structural breaks, leading to compromised results. In the second paper, significant evidence for the existence of structural breaks was found in the case of both variables as well as in the overall relationship. Using the most significant structural break as a breakpoint and investigating the relationship preceding and subsequent to the break pointed to clear evidence that the relationship does change over time. As previous studies have generally assumed the series do not contain breaks, the assumption of time-invariance in previous work may have led to inherently flawed conclusions. However, what this second paper was able to demonstrate, was that even when accounting for breaks, equities maintained their capacity to act as a hedge against inflation in South Africa on either side of that structural break. Further, cointegration testing allowing for structural breaks indicated that the overall relationship was significant and positive and affirmed the prior conclusion that equities are an effective inflationary hedge in the long-run. That is, even when relaxing the assumption of time-invariance and accounting for structural breaks, the overall conclusion for the South African case – that equities are able to perform a hedging function against inflation – remains true. This thesis then continues by developing on this idea of addressing the previous assumptions that may affect this type of analysis, building towards a final, more robust, conclusion. Two additional assumptions remain which require consideration. In recent literature the question of asymmetric adjustment has arisen, including in the analysis of the relationship between equity returns and inflation. Such studies have aimed to deal with the idea that there is no compelling reason to assume that adjustments of the relationship between equity returns and inflation have necessarily been symmetric. Further, it is possible that the relationship may have been subject to a threshold effect, where it exhibits different characteristics depending on whether stocks are underpriced or overpriced relative to goods. It was shown that the adjustment coefficients differ substantially depending on whether they are above or below a certain threshold, and thus that the assumption of linear adjustment is flawed as the relationship exhibits asymmetric adjustment in reality. Further testing for asymmetric adjustment and allowing for such adjustments in the relationship led to the conclusion that the relationship has experienced asymmetric adjustment over the sample period and that the relationship between equity returns and inflation is more appropriately modelled using threshold cointegration techniques. Such findings drastically improve our understanding of the dynamics of the equity returns-inflation relationship and emphasize the importance of accounting for these factors in similar studies. The weakness in previous cointegration testing is somewhat exposed by the strength of the evidence of asymmetric adjustment and effectively questions the findings of the majority of the previous literature which has relied on these techniques. The model far more accurately estimates the relationship between equity returns and inflation and provides new evidence that it experiences a measure of variance around an endogenously determined threshold. Due to the relative power of the model as well as the fact that it has accounted for these factors it can be stated with far greater certainty that South African equities are able to provide an effective hedge against domestic inflation. The evidence of threshold effects is of importance to investors and policy makers, as it is at this point that the adjustment coefficients will vary in terms of their response to exogenous shocks. This is particularly important in the context of this thesis because of the evidence of multiple structural breaks in the cointegrating relationship (found in the second publication) indicating that the relationship has been affected by exogenous shocks at multiple points over the sample period. These factors, namely structural breaks, threshold effects and asymmetric adjustment, are a likely reason why previous studies, on an international scale, have exhibited such conflicting results. Should these studies be reconsidered to incorporate such effects, it would vastly improve the robustness of the results of these studies. It should be noted that the magnitude of the relationship is likely to differ across countries and time periods due to the variation in structural dynamics and macroeconomic conditions. It is therefore improbable that some standard measure of the relationship, such as the conventional theory by Fisher, would accurately estimate the relationship regardless of the sample country or sample period, given the findings in this thesis that the relationship is affected by exogenous factors. Due to the findings of asymmetric adjustment in the third research paper, it is not only the magnitude of the relationship that will cause varied responses, but also potentially the direction of the adjustment. This is investigated further in the fourth paper of this thesis, which aims to disaggregate the overall adjustment coefficient in order to better understand the effects of positive and negative adjustments when they differ substantially from the long-term aggregate relationship. Disaggregating the overall adjustment coefficient into its positive and negative components provided a novel understanding of the dynamics of the relationship. The results of the disaggregation were surprising due to the magnitude of the disparity between the positive and negative adjustments coefficients and indicated that it is important to consider the possibility of imminent fluctuations in inflation when best deciding how to hedge against it. Collectively however, this thesis has proven that equities are able to function as an effective long-run hedge against inflation in South Africa. Further this thesis demonstrates that the inherent assumptions in conventional cointegration techniques, especially those of time-invariance and symmetric adjustment are flawed and have likely contributed to the disparities in the previous literature

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Introduction to special issue:New Times Revisited: Britain in the 1980s

The authors in this volume are collectively engaged with a historical puzzle: What happens if we examine the decade once we step out of the shadows cast by Thatcher? That is, does the decade of the 1980s as a significant and meaningful periodisation (equivalent to that of the 1960s) still work if Thatcher becomes but one part of the story rather than the story itself? The essays in this collection suggest that the 1980s only makes sense as a political period. They situate the 1980s within various longer term trajectories that show the events of the decade to be as much the consequence as the cause of bigger, long-term historical processes. This introduction contextualises the collection within the wider literature, before explaining the collective and individual contributions made

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Mutational analysis of the β-subunit of yeast geranylgeranyl transferase I

The gene CAL1 (also known as CDC43 ) of Saccharomyces cerevisiae encodes the β subunit of geranylgeranyl transferase I (GGTase I), which modifies several small GTPases. Biochemical analyses of the mutant-enzymes encoded by cal1 , and cdc43-2 to cdc43-7 , expressed in bacteria, have hown that all of the mutant enzymes possess reduced activity, and that none shows temerature-sensitive enzymatic activities. Nonetheless, all of the cal1/cdc43 mutants show temperature-sensitive growth phenotypes. Increase in soluble pools of the small GTPases was observed in the yeast mutant cells at the restrictive temperature in vivo, suggesting that the yeast prenylation pathway itself is temperative sensitive. The cal-1 mutation, located most proximal to the C-terminus of the protein, differs from the other cdc43 mutations in several respects. An increase in soluble Rholp was observed in the cal-1 strain grown at the restrictive temperature. The temperature-sensitive phenotype of cal-1 is most efficiently suppressed by overproduction of Rholp. Overproduction of the other essential target, Cdc42p, in contrast, is deleterious in cal-1 cells, but not in other cdc43 mutants or the wild-type strains. The cdc43-5 mutant cells accumulate Cdc42p in soluble pools and cdc43-5 is suppressed by overproduction of Cdc42p. Thus, several phenotypic differences are observed among the cal1/cdc43 mutations, possibly due to alterations in substrate specificity caused by the mutations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42258/1/438-252-1-2-1_62520001.pd

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation